Publications
Publications dans des périodiques internationaux à comité de lecture
Catabolic Pathway of Gamma-caprolactone in the Biocontrol Agent Rhodococcus erythropolis
Corinne Barbey, Alexandre Crépin, Amélie Cirou, Aurélie Budin-Verneuil, Nicole Orange, Marc Feuilloley, Denis Faure, Yves Dessaux, Jean-François Burini, and Xavier Latour
Gamma-caprolactone (GCL) is well-known as a food flavor and has been recently described as a biostimulant molecule promoting the growth of bacteria with biocontrol activity against soft-rot pathogens. Among these biocontrol agents, Rhodococcus erythropolis, characterized by a remarkable metabolic versatility, assimilates various γ-butyrolactone molecules with a branched-aliphatic chain, such as GCL. The assimilative pathway of GCL in R. erythropolis was investigated by two-dimensional gel electrophoresis coupled to matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) analysis. This analysis suggests the involvement of the lactonase QsdA in ring-opening, a feature confirmed by heterologous expression in Escherichia coli. According to proteome analysis, the open-chain form of GCL was degraded by β- and ω-oxidation coupled to the Krebs cycle and β-ketoadipate pathway. Ubiquity of qsdA gene among environmental R. erythropolis isolates was verified by PCR. In addition to a previous N-acyl homoserine lactone catabolic function, QsdA may therefore be involved in an intermediate degradative step of cyclic recalcitrant molecules or in synthesis of flavoring lactones.
Journal of Proteome Research 2012 11 (1), 206-216
doi: 10.1021/pr200936q
http://dx.doi.org/10.1111/j.1574-6941.2010.01023.x
Biological control of pathogen communication in the rhizosphere: A novel approach applied to potato soft rot due to Pectobacterium atrosepticum
Alexandre Crépin, Corinne Barbey, Amélie Cirou, Mélanie Tannières, Nicole Orange, Marc Feuilloley, Yves Dessaux, Jean-François Burini, Denis Faure and Xavier Latour
Plant and Soil, Online First™, 8 November 2011
http://www.springerlink.com/content/70544342q6m31864/fulltext.pdf
Alkanols and chlorophenols cause different physiological adaptive responses on the level of cell surface properties and membrane vesicle formation in Pseudomonas putida DOT-T1E
Baumgarten T., Vazquez J., Bastisch C., Veron W., Feuilloley M.G., Nietzsche S., Wick L.Y., Heipieper H.J.
Appl Microbiol Biotechnol.(in press).
C-type natriuretic peptide (CNP) modulates quorum sensing molecule and toxin productions in Pseudomonas aeruginosa.
Blier A-S., Veron W., Bazire A., Gerault E., Taupin L., Vieillard J., Rehel K., Dufour A., Le Derf F., Orange N., Hulen C., Feuilloley M.G.J., Lesouhaitier O
Microbiology 157:1929-1944
Mechanism of Bactericidal Activity of Microcin L in Escherichia coli and Salmonella enterica.
Morin N., Lanneluc I., Connil N., Cottenceau M., Pons AM., Sablé S. (2011)
Antimicrob Agents Chemother. 55(3):997-1007.
Novel application of cyclolipopeptide amphisin: faisability study as additive to remediate PAHs contaminated sediments.
Groboillot A., Koltalo F., Lederf F., Feuilloley M., Orange N., Poc C.
Int. J. Mol. Sci. 12: 1787-1806
Structural and functional evolution of the translocator protein (18 kDa).
Fan J., Lindemann P., Feuilloley M., Papadopoulos V.
Current Mol. Med
(In press)
OprF is a major actor in the virulence of Pseudomonas aeruginosa.
Fito-Boncompte L., Chapalain A., Bouffartigues E., Chaker H., Lesouhaitier O., Gicquel G., Bazire A., Madi A., Connil N., Véron W., Taupin L., Toussaint B., Cornelis P., Wei Q., Shioya K., Deziel E., Feuilloley M., Orange N., Dufour A., Chevalier S.
Infect. Immun. 79:1176-1186
Mechanisms and recent advances in biological control mediated through the potato rhizosphere
Diallo, S., Crépin, A., Barbey, C., Orange, N., Burini, J.-F. and Latour, X
Potato cultivation has a strategic role as a food source for the human population. Its promising future development relies on improving the control of the numerous microbial diseases that affect its growth. Numerous and recent studies on the potato rhizosphere, mycorrhizosphere and endorhiza reveal the presence of a diverse and dense microflora. This microflora constitutes a rich source for plant growth promoting rhizobacteria and biocontrol agents. So far, the beneficial effects achieved are related to microbial siderophores, antibiotics, biosynthesis of surfactants and phytohormones, nutrient and spatial competition, mycoparasitism, induced systemic resistance, phage therapy, quorum quenching and construction of transgenic lines. Considering the crucial role for food and the diversity of mechanisms involved in growth promotion and microbial protection, the potato constitutes a historical and accurate model in developing new biocontrol strategies.
FEMS Microbiol Ecol 75 (2011) 351–364
doi: 10.1111/j.1742-4658.2007.06109.x
http://dx.doi.org/10.1111/j.1574-6941.2010.01023.x
Growing insights into the safety of bacteriocins: the case of enterocin S37.
Belguesmia Y., Madi A., Sperandio D., Merieau A., Feuilloley M., Prevost H., Dridier D., Connil N.
Very few studies have been reported on the cytotoxicity and impact of bacteriocins, and especially enterocins, upon eukaryotic cells. In order to gain more information on the safety of bacteriocins, we focused this study on enterocin S37, a bacteriocin produced by Enterococcus faecalis S37. We observed dose-dependent cytotoxicity toward undifferentiated Caco-2/TC7 cells. Moreover, no significant effect on differentiated monolayer Caco-2/TC7 and no apoptotic features were observed when cells were treated with 10 mg/ml of enterocin S37. The results obtained indicate possible safe use of enterocin S37 in the gastrointestinal tract of animals to prevent pathogen invasion and/or infection
Research in Microbiology 162 (2011) 159-163
doi:10.1016/j.resmic.2010.09.019
http://www.sciencedirect.com/science/article/pii/S092325081000224X
Revues sur invitation et chapitres d'ouvrages
Les bactéries, leur monde et nous : vers une biologie intégrative et dynamique.
Guespin-Michel J.
Collection: UniverSciences, Dunod/La Recherche Edité le 22 avril 2011
.
Déséquestration de polluants de type hydrocarbures aromatiques polycycliques à l'interface de sédiments au moyen d'un tensio-actif original d'origine biologique
Portet-Koltalo F., Tahar Ammani M., Benamar A., Groboillot A., Orange N., Duclairoir Poc C. (2011)
Specta Analyse, 278, 21-27.
Catabolic Pathway of Gamma-caprolactone in the Biocontrol Agent Rhodococcus erythropolis
Corinne Barbey, Alexandre Crépin, Amélie Cirou, Aurélie Budin-Verneuil, Nicole Orange, Marc Feuilloley, Denis Faure, Yves Dessaux, Jean-François Burini, and Xavier Latour
Gamma-caprolactone (GCL) is well-known as a food flavor and has been recently described as a biostimulant molecule promoting the growth of bacteria with biocontrol activity against soft-rot pathogens. Among these biocontrol agents, Rhodococcus erythropolis, characterized by a remarkable metabolic versatility, assimilates various γ-butyrolactone molecules with a branched-aliphatic chain, such as GCL. The assimilative pathway of GCL in R. erythropolis was investigated by two-dimensional gel electrophoresis coupled to matrix-assisted laser desorption ionization (MALDI) mass spectrometry (MS) analysis. This analysis suggests the involvement of the lactonase QsdA in ring-opening, a feature confirmed by heterologous expression in Escherichia coli. According to proteome analysis, the open-chain form of GCL was degraded by β- and ω-oxidation coupled to the Krebs cycle and β-ketoadipate pathway. Ubiquity of qsdA gene among environmental R. erythropolis isolates was verified by PCR. In addition to a previous N-acyl homoserine lactone catabolic function, QsdA may therefore be involved in an intermediate degradative step of cyclic recalcitrant molecules or in synthesis of flavoring lactones.
Journal of Proteome Research 2012 11 (1), 206-216
doi: 10.1021/pr200936q
http://dx.doi.org/10.1111/j.1574-6941.2010.01023.x
Biological control of pathogen communication in the rhizosphere: A novel approach applied to potato soft rot due to Pectobacterium atrosepticum
Alexandre Crépin, Corinne Barbey, Amélie Cirou, Mélanie Tannières, Nicole Orange, Marc Feuilloley, Yves Dessaux, Jean-François Burini, Denis Faure and Xavier Latour
Plant and Soil, Online First™, 8 November 2011
http://www.springerlink.com/content/70544342q6m31864/fulltext.pdf
Alkanols and chlorophenols cause different physiological adaptive responses on the level of cell surface properties and membrane vesicle formation in Pseudomonas putida DOT-T1E
Baumgarten T., Vazquez J., Bastisch C., Veron W., Feuilloley M.G., Nietzsche S., Wick L.Y., Heipieper H.J.
Appl Microbiol Biotechnol.(in press).
C-type natriuretic peptide (CNP) modulates quorum sensing molecule and toxin productions in Pseudomonas aeruginosa.
Blier A-S., Veron W., Bazire A., Gerault E., Taupin L., Vieillard J., Rehel K., Dufour A., Le Derf F., Orange N., Hulen C., Feuilloley M.G.J., Lesouhaitier O
Microbiology 157:1929-1944
Mechanism of Bactericidal Activity of Microcin L in Escherichia coli and Salmonella enterica.
Morin N., Lanneluc I., Connil N., Cottenceau M., Pons AM., Sablé S. (2011)
Antimicrob Agents Chemother. 55(3):997-1007.
Novel application of cyclolipopeptide amphisin: faisability study as additive to remediate PAHs contaminated sediments.
Groboillot A., Koltalo F., Lederf F., Feuilloley M., Orange N., Poc C.
Int. J. Mol. Sci. 12: 1787-1806
Structural and functional evolution of the translocator protein (18 kDa).
Fan J., Lindemann P., Feuilloley M., Papadopoulos V.
Current Mol. Med
(In press)
OprF is a major actor in the virulence of Pseudomonas aeruginosa.
Fito-Boncompte L., Chapalain A., Bouffartigues E., Chaker H., Lesouhaitier O., Gicquel G., Bazire A., Madi A., Connil N., Véron W., Taupin L., Toussaint B., Cornelis P., Wei Q., Shioya K., Deziel E., Feuilloley M., Orange N., Dufour A., Chevalier S.
Infect. Immun. 79:1176-1186
Mechanisms and recent advances in biological control mediated through the potato rhizosphere
Diallo, S., Crépin, A., Barbey, C., Orange, N., Burini, J.-F. and Latour, X
Potato cultivation has a strategic role as a food source for the human population. Its promising future development relies on improving the control of the numerous microbial diseases that affect its growth. Numerous and recent studies on the potato rhizosphere, mycorrhizosphere and endorhiza reveal the presence of a diverse and dense microflora. This microflora constitutes a rich source for plant growth promoting rhizobacteria and biocontrol agents. So far, the beneficial effects achieved are related to microbial siderophores, antibiotics, biosynthesis of surfactants and phytohormones, nutrient and spatial competition, mycoparasitism, induced systemic resistance, phage therapy, quorum quenching and construction of transgenic lines. Considering the crucial role for food and the diversity of mechanisms involved in growth promotion and microbial protection, the potato constitutes a historical and accurate model in developing new biocontrol strategies.
FEMS Microbiol Ecol 75 (2011) 351–364
doi: 10.1111/j.1742-4658.2007.06109.x
http://dx.doi.org/10.1111/j.1574-6941.2010.01023.x
Growing insights into the safety of bacteriocins: the case of enterocin S37.
Belguesmia Y., Madi A., Sperandio D., Merieau A., Feuilloley M., Prevost H., Dridier D., Connil N.
Very few studies have been reported on the cytotoxicity and impact of bacteriocins, and especially enterocins, upon eukaryotic cells. In order to gain more information on the safety of bacteriocins, we focused this study on enterocin S37, a bacteriocin produced by Enterococcus faecalis S37. We observed dose-dependent cytotoxicity toward undifferentiated Caco-2/TC7 cells. Moreover, no significant effect on differentiated monolayer Caco-2/TC7 and no apoptotic features were observed when cells were treated with 10 mg/ml of enterocin S37. The results obtained indicate possible safe use of enterocin S37 in the gastrointestinal tract of animals to prevent pathogen invasion and/or infection
Research in Microbiology 162 (2011) 159-163
doi:10.1016/j.resmic.2010.09.019
http://www.sciencedirect.com/science/article/pii/S092325081000224X
Revues sur invitation et chapitres d'ouvrages
Les bactéries, leur monde et nous : vers une biologie intégrative et dynamique.
Guespin-Michel J.
Collection: UniverSciences, Dunod/La Recherche Edité le 22 avril 2011
.
Déséquestration de polluants de type hydrocarbures aromatiques polycycliques à l'interface de sédiments au moyen d'un tensio-actif original d'origine biologique
Portet-Koltalo F., Tahar Ammani M., Benamar A., Groboillot A., Orange N., Duclairoir Poc C. (2011)
Specta Analyse, 278, 21-27.
Publications dans des périodiques internationaux à comité de lecture
The Sigma Factor AlgU Plays a Key Role in Formation of Robust Biofilms by Nonmucoid Pseudomonas aeruginosa
Alexis Bazire, Kouki Shioya, Emmanuelle Soum-Soutéra, Emeline Bouffartigues, Cynthia Ryder, Linda Guentas-Dombrowsky, Gaëlle Hémery, Isabelle Linossier, Sylvie Chevalier, Daniel J. Wozniak, Olivier Lesouhaitier, and Alain Dufour
The extracytoplasmic function sigma factor AlgU of Pseudomonas aeruginosa is responsible for alginate overproduction, leading to mucoidy and chronic infections of cystic fibrosis patients. We investigated here the role of AlgU in the formation of nonmucoid biofilms. The algU mutant of P. aeruginosa PAO1 (PAOU) showed a dramatic impairment in biofilm formation under dynamic conditions. PAOU was defective both in cell attachment to glass and in development of robust, shear-resistant biofilms. This was explained by an impaired production of extracellular matrix, specifically of the exopolysaccharide Psl, as revealed by microscopy and enzyme-linked immunosorbent assay. Complementing the algU mutation with a plasmid-borne algU gene restored wild-type phenotypes. Compared with that in PAO1, expression of the psl operon was reduced in the PAOU strain, and the biofilm formation ability of this strain was partially restored by inducing the transcription of the psl operon. Furthermore, expression of the lectin-encoding lecA and lecB genes was reduced in the PAOU strain. In agreement with the requirement of LecB for type IV pilus biogenesis, PAOU displayed impaired twitching motility. Collectively, these genetic downregulation events explain the biofilm formation defect of the PAOU mutant. Promoter mapping indicated that AlgU is probably not directly responsible for transcription of the psl operon and the lec genes, but AlgU is involved in the expression of the ppyR gene, whose product was reported to positively control psl expression. Expressing the ppyR gene in PAOU partially restored the formation of robust biofilms.
Journal of Bacteriology, June 2010, p. 3001-3010, Vol. 192, No. 12
doi: 10.1128/JB.01633-09
http://jb.asm.org/cgi/content/full/192/12/3001?view=long&pmid=20348252
Cell-associated hemolysis activity in the clinical strain of Pseudomonas fluorescens MFN1032
Sperandio D, Rossignol G, Guerillon J, Connil N, Orange N, Feuilloley MG, Merieau A
MFN1032 is a clinical Pseudomonas fluorescens strain able to grow at 37°C. MFN1032 cells induce necrosis and apoptosis in rat glial cells at this temperature. This strain displays secretion-mediated hemolytic activity involving phospholipase C and cyclolipopeptides. Under laboratory conditions, this activity is not expressed at 37°C. This activity is tightly regulated and is subject to phase variation.
BMC Microbiol. 2010; 10: 124
doi: 10.1186/1471-2180-10-124
http://www.biomedcentral.com/1471-2180/10/124
Bacterial-based additives for the production of artificial snow: What are the risks to human health?
A. Lagriffoul, J.L. Boudenne, R. Absi, J.J. Ballet, J.M. Berjeaud, S. Chevalier, E.E. Creppy, E. Gilli, J.P. Gadonna, P. Gadonna-Widehem, C.E. Morris and S. Zini
For around two decades, artificial snow has been used by numerous winter sports resorts to ensure good snow cover at low altitude areas or more generally, to lengthen the skiing season. Biological additives derived from certain bacteria are regularly used to make artificial snow. However, the use of these additives has raised doubts concerning the potential impact on human health and the environment. In this context, the French health authorities have requested the French Agency for Environmental and Occupational Health Safety (Afsset) to assess the health risks resulting from the use of such additives. The health risk assessment was based on a review of the scientific literature, supplemented by professional consultations and expertise. Biological or chemical hazards from additives derived from the ice nucleation active bacterium Pseudomonas syringae were characterised. Potential health hazards to humans were considered in terms of infectious, toxic and allergenic capacities with respect to human populations liable to be exposed and the means of possible exposure. Taking into account these data, a qualitative risk assessment was carried out, according to four exposure scenarios, involving the different populations exposed, and the conditions and routes of exposure. It was concluded that certain health risks can exist for specific categories of professional workers (mainly snowmakers during additive mixing and dilution tank cleaning steps, with risks estimated to be negligible to low if workers comply with safety precautions). P. syringae does not present any pathogenic capacity to humans and that the level of its endotoxins found in artificial snow do not represent a danger beyond that of exposure to P. syringae endotoxins naturally present in snow. However, the risk of possible allergy in some particularly sensitive individuals cannot be excluded. Another important conclusion of this study concerns use of poor microbiological water quality to make artificial snow.
Science of The Total Environment, Volume 408, Issue 7, 1 March 2010, Pages 1659-1666
doi: 10.1016/j.scitotenv.2010.01.009
http://linkinghub.elsevier.com/retrieve/pii/S0048969710000112
The clinical Pseudomonas fluorescens MFN1032 strain exerts a cytotoxic effect on epithelial intestinal cells and induces Interleukin-8 via the AP-1 signaling pathway
Madi A, Lakhdari O, Blottière HM, Guyard-Nicodème M, Le Roux K, Groboillot A, Svinareff P, Doré J, Orange N, Feuilloley MG, Connil N.
Pseudomonas fluorescens is present in low number in the intestinal lumen and has been proposed to play a role in Crohn's disease (CD). Indeed, a highly specific antigen, I2, has been detected in CD patients and correlated to the severity of the disease. We aimed to determine whether P. fluorescens was able to adhere to human intestinal epithelial cells (IECs), induce cytotoxicity and activate a proinflammatory response
BMC Microbiology 2010, 10:215
doi:10.1186/1471-2180-10-215
www.biomedcentral.com/1471-2180/10/215
Toxicity induced by cumene hydroperoxide in PC12 cells: Protective role of thiol donors
F Vimard, M Saucet, O Nicole, M Feuilloley, D Duval
Oxidative shock and production of reactive oxygen species are known to play a major role in situations leading to neuron degeneration, but the precise mechanisms responsible for cell degeneration remain uncertain. In the present article, we have studied in PC 12 cells the effect of cumene hydroxyperoxide on both cell metabolism and morphology. We observed that relatively low concentrations of the drug (100 μM) led to a significant decrease in the cellular content of ATP and reduced glutathione as well as to a decreased mitochondrial potential. These metabolic alterations were followed by an important increase in intracellular free calcium and membrane disruption and death. In parallel, we observed profound changes in cell morphology with a shortening of cell extensions, the formation of ruffles and blebs at the cell surface, and a progressive detachment of the cells from the surface of the culture flasks. We also showed that addition of thiol donors such as N-acetylcysteine or β-mercaptoethanol, which were able to enhance cell glutathione content, almost completely protected PC 12 cells from the toxic action of cumene hydroperoxide whereas pretreatment by buthionine sulfoximine, a selective inhibitor of GSH synthesis, enhanced its action.
Journal of Biochemical and Molecular Toxicology
Article first published online: 1 DEC 2010
doi:10.1002/jbt.20377
http://onlinelibrary.wiley.com/doi/10.1002/jbt.20377/abstract
Effectiveness of Pulsed Ultraviolet-Light Treatment for Bacterial Inactivation on Agar Surface and Liquid Medium
Noura Elmnasser Ben Saïd, Michel Federighi, Amina Bakhrouf, Nicole Orange
In the present study, the efficiency of a broad-spectrum pulsed ultraviolet (UV)-light for the inactivation of Listeria monocytogenes Scott A, L. monocytogenes CNL 895807, and Pseudomonas fluorescens MF37 populations as agar seeded or suspended cells was investigated. The bacterial populations were treated by pulsed UV-light at different number of pulses (1 to 3), dose of energy (162, 243, or 324J), and distance from the strobe (4, 9, or 12cm). After pulsed UV-light treatment, the bacterial reduction was determined by standard plate count. The results showed that there was a significant reduction of population along with an increase of light energy and number of pulses. Decreasing the distance between the Petri dishes and the xenon lamp demonstrated an increase in bacterial reduction. Decontamination efficacy decreased significantly with the increase in level of contamination. This study demonstrates that pulsed UV-light can be used as an effective sterilizing method
Journal of Biochemical and Molecular Toxicology
Foodborne Pathogens and Disease. November 2010, 7(11): 1401-1406.
doi:10.1089/fpd.2010.0594
http://dx.doi.org/10.1089/fpd.2010.0594
Pseudomonas fluorescens alters epithelial permeability and translocates across Caco-2/TC7 intestinal cells.
Madi, Amar, Svinareff, Pascal, Orange, Nicole, Feuilloley, Marc Gj, Connil, Nathalie.
BACKGROUND: Pseudomonas fluorescens has long been considered as a psychrotrophic microorganism. Recently, we have shown that clinical strains of P. fluorescens (biovar 1) are able to adapt at a growth temperature of 37°C or above and induce a specific inflammatory response. Interestingly, a highly specific antigen of P. fluorescens, I2, is detected in the serum of patients with Crohn's disease but the possible role of this bacterium in the disease has not yet been explored. In the present study, we examined the ability of a psychrotrophic and a clinical strain of P. fluorescens to modulate the permeability of a Caco-2/TC7 intestinal epithelial model, reorganize the actin cytoskeleton, invade the target cells and translocate across the epithelium. The behaviour of these two strains was compared to that of the well known opportunistic pathogen P. aeruginosa PAO1.
RESULTS: Both strains of P. fluorescens were found to decrease the transepithelial resistance (TER) of Caco-2/TC7 differentiated monolayers. This was associated with an increase in paracellular permeability and F-actin microfilaments rearrangements. Moreover, the invasion and translocation tests demonstrated that the two strains used in this study can invade and translocate across the differentiated Caco-2/TC7 cell monolayers.
CONCLUSIONS: The present work shows for the first time, that P. fluorescens is able to alter the intestinal epithelial barrier function by disorganizing the F-actin microfilament network. Moreover, we reveal that independently of their origins, the two P. fluorescens strains can translocate across differentiated Caco-2/TC7 cell monolayers by using the transcellular pathway. These findings could, at least in part, explain the presence of the P. fluorescens specific I2 antigen in the serum of patients with Crohn's disease.
Gut pathogens (2010) vol. 2 (1) pp. 16
doi:10.1186/1757-4749-2-16
http://www.gutpathogens.com/content/2/1/16
Revues sur invitation et chapitres d'ouvrages
Portet-Koltalo F., Tahar Ammani M., Benamar A., Groboillot A., Duclairoir Poc C. Orange N. (2010)
Pollution des sédiments de dragage Procédés de bioremédiation alliés à l'électromigration,
Specta Analyse, 277, 54-57.
The Sigma Factor AlgU Plays a Key Role in Formation of Robust Biofilms by Nonmucoid Pseudomonas aeruginosa
Alexis Bazire, Kouki Shioya, Emmanuelle Soum-Soutéra, Emeline Bouffartigues, Cynthia Ryder, Linda Guentas-Dombrowsky, Gaëlle Hémery, Isabelle Linossier, Sylvie Chevalier, Daniel J. Wozniak, Olivier Lesouhaitier, and Alain Dufour
The extracytoplasmic function sigma factor AlgU of Pseudomonas aeruginosa is responsible for alginate overproduction, leading to mucoidy and chronic infections of cystic fibrosis patients. We investigated here the role of AlgU in the formation of nonmucoid biofilms. The algU mutant of P. aeruginosa PAO1 (PAOU) showed a dramatic impairment in biofilm formation under dynamic conditions. PAOU was defective both in cell attachment to glass and in development of robust, shear-resistant biofilms. This was explained by an impaired production of extracellular matrix, specifically of the exopolysaccharide Psl, as revealed by microscopy and enzyme-linked immunosorbent assay. Complementing the algU mutation with a plasmid-borne algU gene restored wild-type phenotypes. Compared with that in PAO1, expression of the psl operon was reduced in the PAOU strain, and the biofilm formation ability of this strain was partially restored by inducing the transcription of the psl operon. Furthermore, expression of the lectin-encoding lecA and lecB genes was reduced in the PAOU strain. In agreement with the requirement of LecB for type IV pilus biogenesis, PAOU displayed impaired twitching motility. Collectively, these genetic downregulation events explain the biofilm formation defect of the PAOU mutant. Promoter mapping indicated that AlgU is probably not directly responsible for transcription of the psl operon and the lec genes, but AlgU is involved in the expression of the ppyR gene, whose product was reported to positively control psl expression. Expressing the ppyR gene in PAOU partially restored the formation of robust biofilms.
Journal of Bacteriology, June 2010, p. 3001-3010, Vol. 192, No. 12
doi: 10.1128/JB.01633-09
http://jb.asm.org/cgi/content/full/192/12/3001?view=long&pmid=20348252
Cell-associated hemolysis activity in the clinical strain of Pseudomonas fluorescens MFN1032
Sperandio D, Rossignol G, Guerillon J, Connil N, Orange N, Feuilloley MG, Merieau A
MFN1032 is a clinical Pseudomonas fluorescens strain able to grow at 37°C. MFN1032 cells induce necrosis and apoptosis in rat glial cells at this temperature. This strain displays secretion-mediated hemolytic activity involving phospholipase C and cyclolipopeptides. Under laboratory conditions, this activity is not expressed at 37°C. This activity is tightly regulated and is subject to phase variation.
BMC Microbiol. 2010; 10: 124
doi: 10.1186/1471-2180-10-124
http://www.biomedcentral.com/1471-2180/10/124
Bacterial-based additives for the production of artificial snow: What are the risks to human health?
A. Lagriffoul, J.L. Boudenne, R. Absi, J.J. Ballet, J.M. Berjeaud, S. Chevalier, E.E. Creppy, E. Gilli, J.P. Gadonna, P. Gadonna-Widehem, C.E. Morris and S. Zini
For around two decades, artificial snow has been used by numerous winter sports resorts to ensure good snow cover at low altitude areas or more generally, to lengthen the skiing season. Biological additives derived from certain bacteria are regularly used to make artificial snow. However, the use of these additives has raised doubts concerning the potential impact on human health and the environment. In this context, the French health authorities have requested the French Agency for Environmental and Occupational Health Safety (Afsset) to assess the health risks resulting from the use of such additives. The health risk assessment was based on a review of the scientific literature, supplemented by professional consultations and expertise. Biological or chemical hazards from additives derived from the ice nucleation active bacterium Pseudomonas syringae were characterised. Potential health hazards to humans were considered in terms of infectious, toxic and allergenic capacities with respect to human populations liable to be exposed and the means of possible exposure. Taking into account these data, a qualitative risk assessment was carried out, according to four exposure scenarios, involving the different populations exposed, and the conditions and routes of exposure. It was concluded that certain health risks can exist for specific categories of professional workers (mainly snowmakers during additive mixing and dilution tank cleaning steps, with risks estimated to be negligible to low if workers comply with safety precautions). P. syringae does not present any pathogenic capacity to humans and that the level of its endotoxins found in artificial snow do not represent a danger beyond that of exposure to P. syringae endotoxins naturally present in snow. However, the risk of possible allergy in some particularly sensitive individuals cannot be excluded. Another important conclusion of this study concerns use of poor microbiological water quality to make artificial snow.
Science of The Total Environment, Volume 408, Issue 7, 1 March 2010, Pages 1659-1666
doi: 10.1016/j.scitotenv.2010.01.009
http://linkinghub.elsevier.com/retrieve/pii/S0048969710000112
The clinical Pseudomonas fluorescens MFN1032 strain exerts a cytotoxic effect on epithelial intestinal cells and induces Interleukin-8 via the AP-1 signaling pathway
Madi A, Lakhdari O, Blottière HM, Guyard-Nicodème M, Le Roux K, Groboillot A, Svinareff P, Doré J, Orange N, Feuilloley MG, Connil N.
Pseudomonas fluorescens is present in low number in the intestinal lumen and has been proposed to play a role in Crohn's disease (CD). Indeed, a highly specific antigen, I2, has been detected in CD patients and correlated to the severity of the disease. We aimed to determine whether P. fluorescens was able to adhere to human intestinal epithelial cells (IECs), induce cytotoxicity and activate a proinflammatory response
BMC Microbiology 2010, 10:215
doi:10.1186/1471-2180-10-215
www.biomedcentral.com/1471-2180/10/215
Toxicity induced by cumene hydroperoxide in PC12 cells: Protective role of thiol donors
F Vimard, M Saucet, O Nicole, M Feuilloley, D Duval
Oxidative shock and production of reactive oxygen species are known to play a major role in situations leading to neuron degeneration, but the precise mechanisms responsible for cell degeneration remain uncertain. In the present article, we have studied in PC 12 cells the effect of cumene hydroxyperoxide on both cell metabolism and morphology. We observed that relatively low concentrations of the drug (100 μM) led to a significant decrease in the cellular content of ATP and reduced glutathione as well as to a decreased mitochondrial potential. These metabolic alterations were followed by an important increase in intracellular free calcium and membrane disruption and death. In parallel, we observed profound changes in cell morphology with a shortening of cell extensions, the formation of ruffles and blebs at the cell surface, and a progressive detachment of the cells from the surface of the culture flasks. We also showed that addition of thiol donors such as N-acetylcysteine or β-mercaptoethanol, which were able to enhance cell glutathione content, almost completely protected PC 12 cells from the toxic action of cumene hydroperoxide whereas pretreatment by buthionine sulfoximine, a selective inhibitor of GSH synthesis, enhanced its action.
Journal of Biochemical and Molecular Toxicology
Article first published online: 1 DEC 2010
doi:10.1002/jbt.20377
http://onlinelibrary.wiley.com/doi/10.1002/jbt.20377/abstract
Effectiveness of Pulsed Ultraviolet-Light Treatment for Bacterial Inactivation on Agar Surface and Liquid Medium
Noura Elmnasser Ben Saïd, Michel Federighi, Amina Bakhrouf, Nicole Orange
In the present study, the efficiency of a broad-spectrum pulsed ultraviolet (UV)-light for the inactivation of Listeria monocytogenes Scott A, L. monocytogenes CNL 895807, and Pseudomonas fluorescens MF37 populations as agar seeded or suspended cells was investigated. The bacterial populations were treated by pulsed UV-light at different number of pulses (1 to 3), dose of energy (162, 243, or 324J), and distance from the strobe (4, 9, or 12cm). After pulsed UV-light treatment, the bacterial reduction was determined by standard plate count. The results showed that there was a significant reduction of population along with an increase of light energy and number of pulses. Decreasing the distance between the Petri dishes and the xenon lamp demonstrated an increase in bacterial reduction. Decontamination efficacy decreased significantly with the increase in level of contamination. This study demonstrates that pulsed UV-light can be used as an effective sterilizing method
Journal of Biochemical and Molecular Toxicology
Foodborne Pathogens and Disease. November 2010, 7(11): 1401-1406.
doi:10.1089/fpd.2010.0594
http://dx.doi.org/10.1089/fpd.2010.0594
Pseudomonas fluorescens alters epithelial permeability and translocates across Caco-2/TC7 intestinal cells.
Madi, Amar, Svinareff, Pascal, Orange, Nicole, Feuilloley, Marc Gj, Connil, Nathalie.
BACKGROUND: Pseudomonas fluorescens has long been considered as a psychrotrophic microorganism. Recently, we have shown that clinical strains of P. fluorescens (biovar 1) are able to adapt at a growth temperature of 37°C or above and induce a specific inflammatory response. Interestingly, a highly specific antigen of P. fluorescens, I2, is detected in the serum of patients with Crohn's disease but the possible role of this bacterium in the disease has not yet been explored. In the present study, we examined the ability of a psychrotrophic and a clinical strain of P. fluorescens to modulate the permeability of a Caco-2/TC7 intestinal epithelial model, reorganize the actin cytoskeleton, invade the target cells and translocate across the epithelium. The behaviour of these two strains was compared to that of the well known opportunistic pathogen P. aeruginosa PAO1.
RESULTS: Both strains of P. fluorescens were found to decrease the transepithelial resistance (TER) of Caco-2/TC7 differentiated monolayers. This was associated with an increase in paracellular permeability and F-actin microfilaments rearrangements. Moreover, the invasion and translocation tests demonstrated that the two strains used in this study can invade and translocate across the differentiated Caco-2/TC7 cell monolayers.
CONCLUSIONS: The present work shows for the first time, that P. fluorescens is able to alter the intestinal epithelial barrier function by disorganizing the F-actin microfilament network. Moreover, we reveal that independently of their origins, the two P. fluorescens strains can translocate across differentiated Caco-2/TC7 cell monolayers by using the transcellular pathway. These findings could, at least in part, explain the presence of the P. fluorescens specific I2 antigen in the serum of patients with Crohn's disease.
Gut pathogens (2010) vol. 2 (1) pp. 16
doi:10.1186/1757-4749-2-16
http://www.gutpathogens.com/content/2/1/16
Revues sur invitation et chapitres d'ouvrages
Portet-Koltalo F., Tahar Ammani M., Benamar A., Groboillot A., Duclairoir Poc C. Orange N. (2010)
Pollution des sédiments de dragage Procédés de bioremédiation alliés à l'électromigration,
Specta Analyse, 277, 54-57.
Publications dans des périodiques internationaux à comité de lecture
Identification of traits implicated in the rhizosphere competence of fluorescent pseudomonads: description of a strategy based on population and model strain studies.
Xavier Latour, S Delorme, P Mirleau, P Lemanceau..
The lack of consistency of the beneficial effects of inoculated fluorescent pseudomonads has often been related to their bad survival in the rhizosphere. In this review, we describe the strategy followed over the last decade to study traits involved in the rhizosphere competence of these bacteria. The diversity of indigenous populations associated with plant roots was first compared to that of populations associated with uncultivated soils in order to identify traits that discriminate these populations. The involvement of these bacterial traits in the rhizosphere competence was then assessed by comparing the competitiveness of a wild-type strain to that of mutants affected in the corresponding phenotypes. Finally, traits shared by populations adapted to the rhizosphere were identified by comparing both the competitiveness in the rhizosphere and the metabolism of a collection of bacterial strains. The data yielded indicated that rhizosphere competent pseudomonads show a specific metabolism especially characterized by the efficiency of the pyoverdine-mediated iron uptake and by the ability to reduce nitrogen oxides - Sustainable Agriculture (vol. 1) – E. Lichtfouse, M. Navarrete, P. Debaeke, S. Véronique, C. Alberola (Eds.), 285-296 Springer, 919 p. (2009)
doi: 10.1007/978-90-481-2666-8_19
http://www.springerlink.com/content/l418466443t27175/fulltext.pdf
Phenotypic variation in the Pseudomonas fluorescens clinical strain MFN1032.
G Rossignol, D Sperandio, J Guerillon, C Duclairoir Poc, E Soum-Soutera, N Orange, M G J Feuilloley, A Merieau.
Pseudomonas fluorescens is a highly heterogeneous species and includes both avirulent strains and clinical strains involved in nosocomial infections. We previously demonstrated that clinical strain MFN1032 has hemolytic activity involving phospholipase C (PlcC) and biosurfactants (BSs), similar to that of the opportunistic pathogen Pseudomonas aeruginosa. When incubated under specific conditions, MFN1032 forms translucent phenotypic variant colonies defective in hemolysis, but not necessarily in PlcC. We analyzed eight variants of the original strain MFN1032 and found that they clustered into two groups. Mutations of genes encoding the two-component regulatory system GacS/GacA are responsible for phenotypic variation in the first group of variants. These group 1 variants did not produce secondary metabolites and had impaired biofilm formation. The second group was composed of hyperflagellated cells with enhanced biofilm capacity: they did not produce BSs and were thus unable to swarm. Artificial reduction of the intracellular level of c-di-GMP restored the ability to form biofilm to levels shown by the wild type, but production of BSs was still repressed. Phenotypic variation might increase the virulence potential of this strain. - Research in microbiology (2009) vol. 160 (5) pp. 337-44
doi: 10.1016/j.resmic.2009.04.004
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-4W6Y5KS-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=e9240530a072b4592e9a89c4b6368e6f
Simultaneous and selective detection of two major soft rot pathogens of potato: Pectobacterium atrosepticum (Erwinia carotovora subsp. . atrosepticum) and Dickeya spp. (Erwinia chrysanthemi).
S Diallo, X Latour, A Groboillot, B Smadja, Patricia Copin, Nicole Orange.
Dickeya spp. and Pectobacterium atrosep- ticum are major pathogens of potato. Current methods to detect these soft-rotting bacteria require separate identification steps. Here we describe a simple method allowing simultaneous detection of both pathogens based on multiplex PCR. The sensitivity of the primer sets was first examined on purified genomic DNA of the type strains Dickeya chrysanthemi 2048T and P. atrosepticum 1526T. The specificity and detection limits of the primer sets were successfully tested on 61 strains belonging to various Dickeya and Pectobacterium species, on artificially inoculated and on naturally contaminated potato plants. This new method provides a gain in time and materials, the main advantages for large-scale processes such as pathogen-free seed certification. - European Journal of Plant Pathology (2009) (125) pp. 349–354
doi:10.1007/s10658-009-9477-4
http://www.springerlink.com/index/A755368205NGW10G.pdf
Bacterial Ortholog of Mammalian Translocator Protein (TSPO) with Virulence.
A Chapalain, S Chevalier, N Orange, Laurence Murillo, Vassilios Papadopoulos, Marc G J Feuilloley.
The translocator protein (TSPO), previously designated as peripheral-type benzodiazepine receptor, is a protein mainly located in the outer mitochondrial membrane of eukaryotic cells. TSPO is implicated in major physiological functions and functionally associated with other proteins such as the voltage-dependent anionic channel, also designated as mitochondrial porin. Surprisingly, a TSPO-related protein was identified in the photosynthetic bacterium Rhodobacter sphaeroides but it was initially considered as a relict of evolution. In the present study we cloned a tspO gene in Pseudomonas fluorescens MF37, a non-photosynthetic eubacterium and we used bioinformatics tools to identify TSPO in the genome of 97 other bacteria. P. fluorescens TSPO was recognized by antibodies against mouse protein and by PK 11195, an artificial ligand of mitochondrial TSPO. As in eukaryotes, bacterial TSPO appears functionally organized as a dimer and the apparent Kd for PK 11195 is in the same range than for its eukaryotic counterpart. When P. fluorescens MF37 was treated with PK 11195 (1025 M) adhesion to living or artificial surfaces and biofilm formation activity were increased. Conversely, the apoptotic potential of bacteria on eukaryotic cells was significantly reduced. This effect of PK11195 was abolished in a mutant of P. fluorescens MF37 deficient for its major outer membrane porin, OprF. The present results demonstrate the existence of a bacterial TSPO that shares common structural and functional characteristics with its mammalian counterpart. This protein, apparently involved in adhesion and virulence, reveals the existence of a possible new inter kingdom signalling system and suggests that the human microbiome should be involuntarily exposed to the evolutionary pressure of benzodiazepines and related molecules. This discovery also represents a promising opportunity for the development of alternative antibacterial strategies. - PLoS ONE | www.plosone.org (2009) vol. 4 (6)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699550/pdf/pone.0006096.pdf
Revues sur invitation et chapitres d'ouvrages
Pyrogens and bacterial endotoxins: What do we measure ?
Guyard-Nicodème M., Chapalain A., Chevalier S., Veron W., Lesouhaitier O., Tollemer H., Orange N., Feuilloley M.G.J.
Industria Farmaceutica (2009) vol. 148 pp. 97-101
Gram-Negative Bacterial Sensors for Eukaryotic Signal Molecules.
O Lesouhaitier, W Veron, A Chapalain, A Madi, A Blier, A Dagorn, N.Connil, S.Chevalier, N.Orange, M.Feuilloley.
Ample evidence exists showing that eukaryotic signal molecules synthesized and released by the host can activate the virulence of opportunistic pathogens. The sensitivity of prokaryotes to host signal molecules requires the presence of bacterial sensors. These prokaryotic sensors, or receptors, have a double function: stereospecific recognition in a complex environment and transduction of the message in order to initiate bacterial physiological modifications. As messengers are generally unable to freely cross the bacterial membrane, they require either the presence of sensors anchored in the membrane or transporters allowing direct recognition inside the bacterial cytoplasm. Since the discovery of quorum sensing, it was established that the production of virulence factors by bacteria is tightly growth-phase regulated. It is now obvious that expression of bacterial virulence is also controlled by detection of the eukaryotic messengers released in the micro-environment as endocrine or neuro-endocrine modulators. In the presence of host physiological stress many eukaryotic factors are released and detected by Gram-negative bacteria which in return rapidly adapt their physiology. For instance, Pseudomonas aeruginosa can bind elements of the host immune system such as interferon-γ and dynorphin and then through quorum sensing circuitry enhance its virulence. Escherichia coli sensitivity to the neurohormones of the catecholamines family appears relayed by a recently identified bacterial adrenergic receptor. In the present review, we will describe the mechanisms by which various eukaryotic signal molecules produced by host may activate Gram-negative bacteria virulence. Particular attention will be paid to Pseudomonas, a genus whose representative species, P. aeruginosa, is a common opportunistic pathogen. The discussion will be particularly focused on the pivotal role played by these new types of pathogen sensors from the sensing to the transduction mechanism involved in virulence factors regulation. Finally, we will discuss the consequence of the impact of host signal molecules on commensally or opportunistic pathogens associated with different human tissue. - Sensors (2009). 9(9), 6967-6990
doi:10.3390/s90906967
http://dx.doi.org/10.3390/s90906967
Container-Content CompatibilityStudies? A Pharmaceutical Team’s Integrated Approach.
A Laschi, N Sehnal, A Alarcon, B Barcelo, F Caire-Maurisier, M Delaire, M Feuilloley, S Genot, C Lacaze, L Pisarik, C Smati.
PDA Journal of Pharmaceutical Science and Technology (2009) vol. 63 pp. 285-293
Quorum sensing as a target for novel biocontrol strategies.
A Cirou, S Uroz, E Chapelle, X Latour, N Orange, D Faure, Y Dessaux.
Recent Developments in Management of Plant Diseases (Plant Pathology in the 21st Century) Ulrich Gisi, Ilan Chet, M.Lodovica Gullino (eds) (2009) pp. 121-132
Identification of traits implicated in the rhizosphere competence of fluorescent pseudomonads: description of a strategy based on population and model strain studies.
Xavier Latour, S Delorme, P Mirleau, P Lemanceau..
The lack of consistency of the beneficial effects of inoculated fluorescent pseudomonads has often been related to their bad survival in the rhizosphere. In this review, we describe the strategy followed over the last decade to study traits involved in the rhizosphere competence of these bacteria. The diversity of indigenous populations associated with plant roots was first compared to that of populations associated with uncultivated soils in order to identify traits that discriminate these populations. The involvement of these bacterial traits in the rhizosphere competence was then assessed by comparing the competitiveness of a wild-type strain to that of mutants affected in the corresponding phenotypes. Finally, traits shared by populations adapted to the rhizosphere were identified by comparing both the competitiveness in the rhizosphere and the metabolism of a collection of bacterial strains. The data yielded indicated that rhizosphere competent pseudomonads show a specific metabolism especially characterized by the efficiency of the pyoverdine-mediated iron uptake and by the ability to reduce nitrogen oxides - Sustainable Agriculture (vol. 1) – E. Lichtfouse, M. Navarrete, P. Debaeke, S. Véronique, C. Alberola (Eds.), 285-296 Springer, 919 p. (2009)
doi: 10.1007/978-90-481-2666-8_19
http://www.springerlink.com/content/l418466443t27175/fulltext.pdf
Phenotypic variation in the Pseudomonas fluorescens clinical strain MFN1032.
G Rossignol, D Sperandio, J Guerillon, C Duclairoir Poc, E Soum-Soutera, N Orange, M G J Feuilloley, A Merieau.
Pseudomonas fluorescens is a highly heterogeneous species and includes both avirulent strains and clinical strains involved in nosocomial infections. We previously demonstrated that clinical strain MFN1032 has hemolytic activity involving phospholipase C (PlcC) and biosurfactants (BSs), similar to that of the opportunistic pathogen Pseudomonas aeruginosa. When incubated under specific conditions, MFN1032 forms translucent phenotypic variant colonies defective in hemolysis, but not necessarily in PlcC. We analyzed eight variants of the original strain MFN1032 and found that they clustered into two groups. Mutations of genes encoding the two-component regulatory system GacS/GacA are responsible for phenotypic variation in the first group of variants. These group 1 variants did not produce secondary metabolites and had impaired biofilm formation. The second group was composed of hyperflagellated cells with enhanced biofilm capacity: they did not produce BSs and were thus unable to swarm. Artificial reduction of the intracellular level of c-di-GMP restored the ability to form biofilm to levels shown by the wild type, but production of BSs was still repressed. Phenotypic variation might increase the virulence potential of this strain. - Research in microbiology (2009) vol. 160 (5) pp. 337-44
doi: 10.1016/j.resmic.2009.04.004
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-4W6Y5KS-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=e9240530a072b4592e9a89c4b6368e6f
Simultaneous and selective detection of two major soft rot pathogens of potato: Pectobacterium atrosepticum (Erwinia carotovora subsp. . atrosepticum) and Dickeya spp. (Erwinia chrysanthemi).
S Diallo, X Latour, A Groboillot, B Smadja, Patricia Copin, Nicole Orange.
Dickeya spp. and Pectobacterium atrosep- ticum are major pathogens of potato. Current methods to detect these soft-rotting bacteria require separate identification steps. Here we describe a simple method allowing simultaneous detection of both pathogens based on multiplex PCR. The sensitivity of the primer sets was first examined on purified genomic DNA of the type strains Dickeya chrysanthemi 2048T and P. atrosepticum 1526T. The specificity and detection limits of the primer sets were successfully tested on 61 strains belonging to various Dickeya and Pectobacterium species, on artificially inoculated and on naturally contaminated potato plants. This new method provides a gain in time and materials, the main advantages for large-scale processes such as pathogen-free seed certification. - European Journal of Plant Pathology (2009) (125) pp. 349–354
doi:10.1007/s10658-009-9477-4
http://www.springerlink.com/index/A755368205NGW10G.pdf
Bacterial Ortholog of Mammalian Translocator Protein (TSPO) with Virulence.
A Chapalain, S Chevalier, N Orange, Laurence Murillo, Vassilios Papadopoulos, Marc G J Feuilloley.
The translocator protein (TSPO), previously designated as peripheral-type benzodiazepine receptor, is a protein mainly located in the outer mitochondrial membrane of eukaryotic cells. TSPO is implicated in major physiological functions and functionally associated with other proteins such as the voltage-dependent anionic channel, also designated as mitochondrial porin. Surprisingly, a TSPO-related protein was identified in the photosynthetic bacterium Rhodobacter sphaeroides but it was initially considered as a relict of evolution. In the present study we cloned a tspO gene in Pseudomonas fluorescens MF37, a non-photosynthetic eubacterium and we used bioinformatics tools to identify TSPO in the genome of 97 other bacteria. P. fluorescens TSPO was recognized by antibodies against mouse protein and by PK 11195, an artificial ligand of mitochondrial TSPO. As in eukaryotes, bacterial TSPO appears functionally organized as a dimer and the apparent Kd for PK 11195 is in the same range than for its eukaryotic counterpart. When P. fluorescens MF37 was treated with PK 11195 (1025 M) adhesion to living or artificial surfaces and biofilm formation activity were increased. Conversely, the apoptotic potential of bacteria on eukaryotic cells was significantly reduced. This effect of PK11195 was abolished in a mutant of P. fluorescens MF37 deficient for its major outer membrane porin, OprF. The present results demonstrate the existence of a bacterial TSPO that shares common structural and functional characteristics with its mammalian counterpart. This protein, apparently involved in adhesion and virulence, reveals the existence of a possible new inter kingdom signalling system and suggests that the human microbiome should be involuntarily exposed to the evolutionary pressure of benzodiazepines and related molecules. This discovery also represents a promising opportunity for the development of alternative antibacterial strategies. - PLoS ONE | www.plosone.org (2009) vol. 4 (6)
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2699550/pdf/pone.0006096.pdf
Revues sur invitation et chapitres d'ouvrages
Pyrogens and bacterial endotoxins: What do we measure ?
Guyard-Nicodème M., Chapalain A., Chevalier S., Veron W., Lesouhaitier O., Tollemer H., Orange N., Feuilloley M.G.J.
Industria Farmaceutica (2009) vol. 148 pp. 97-101
Gram-Negative Bacterial Sensors for Eukaryotic Signal Molecules.
O Lesouhaitier, W Veron, A Chapalain, A Madi, A Blier, A Dagorn, N.Connil, S.Chevalier, N.Orange, M.Feuilloley.
Ample evidence exists showing that eukaryotic signal molecules synthesized and released by the host can activate the virulence of opportunistic pathogens. The sensitivity of prokaryotes to host signal molecules requires the presence of bacterial sensors. These prokaryotic sensors, or receptors, have a double function: stereospecific recognition in a complex environment and transduction of the message in order to initiate bacterial physiological modifications. As messengers are generally unable to freely cross the bacterial membrane, they require either the presence of sensors anchored in the membrane or transporters allowing direct recognition inside the bacterial cytoplasm. Since the discovery of quorum sensing, it was established that the production of virulence factors by bacteria is tightly growth-phase regulated. It is now obvious that expression of bacterial virulence is also controlled by detection of the eukaryotic messengers released in the micro-environment as endocrine or neuro-endocrine modulators. In the presence of host physiological stress many eukaryotic factors are released and detected by Gram-negative bacteria which in return rapidly adapt their physiology. For instance, Pseudomonas aeruginosa can bind elements of the host immune system such as interferon-γ and dynorphin and then through quorum sensing circuitry enhance its virulence. Escherichia coli sensitivity to the neurohormones of the catecholamines family appears relayed by a recently identified bacterial adrenergic receptor. In the present review, we will describe the mechanisms by which various eukaryotic signal molecules produced by host may activate Gram-negative bacteria virulence. Particular attention will be paid to Pseudomonas, a genus whose representative species, P. aeruginosa, is a common opportunistic pathogen. The discussion will be particularly focused on the pivotal role played by these new types of pathogen sensors from the sensing to the transduction mechanism involved in virulence factors regulation. Finally, we will discuss the consequence of the impact of host signal molecules on commensally or opportunistic pathogens associated with different human tissue. - Sensors (2009). 9(9), 6967-6990
doi:10.3390/s90906967
http://dx.doi.org/10.3390/s90906967
Container-Content CompatibilityStudies? A Pharmaceutical Team’s Integrated Approach.
A Laschi, N Sehnal, A Alarcon, B Barcelo, F Caire-Maurisier, M Delaire, M Feuilloley, S Genot, C Lacaze, L Pisarik, C Smati.
PDA Journal of Pharmaceutical Science and Technology (2009) vol. 63 pp. 285-293
Quorum sensing as a target for novel biocontrol strategies.
A Cirou, S Uroz, E Chapelle, X Latour, N Orange, D Faure, Y Dessaux.
Recent Developments in Management of Plant Diseases (Plant Pathology in the 21st Century) Ulrich Gisi, Ilan Chet, M.Lodovica Gullino (eds) (2009) pp. 121-132
Publications dans des périodiques internationaux à comité de lecture
Comparative study of 7 fluorescent pseudomonad clinical isolates.
A Chapalain, G Rossignol, O Lesouhaitier, A Merieau, C Gruffaz, J Guerillon, J-M Meyer, N Orange, M G J Feuilloley.
There is some debate about the potential survival of Pseudomonas fluorescens at temperatures above 37 degrees C and its consequences for infectious potential, owing to the heterogeneity of clinical strains. Seven clinical strains growing at 37 degrees C or more were submitted for polyphasic identification; 2 were identified as Pseudomonas mosselii and 4 were precisely characterized as P. fluorescens bv. I or II. The binding indexes on glial cells of the strains identified as P. fluorescens bv. I and P. mosselii were compared with that of a reference psychrotrophic strain, P. fluorescens MF37 (bv. V). Clinical P. fluorescens had a similar adherence potential range than strain MF37. Conversely, the binding indexes for P. mosselii strains were 3 times greater than that for strain MF37. These data, and those obtained by comparing the cytotoxic activities of P. fluorescens clinical strains, suggest the existence of different virulence mechanisms, leading either to a low infectious form or to a microorganism with cytotoxic activity in the same range as that of P. mosselii or even Pseudomonas aeruginosa. - Canadian journal of microbiology (2008) vol. 54 (1) pp. 19-27
doi:10.1139/w07-110
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=18388968&retmode=ref&cmd=prlinks
Plasmachemical decolourisation of Bromothymol Blue by gliding electric discharge at atmospheric pressure.
A Doubla, L Bouba Bello, M Fotso, J Brisset.
The colour of aqueous solutions of 3,3′-dibromothymolsulfonephtalein (Bromothymol Blue) fades when they are exposed to a gliding electric discharge, due to the nature of impinging plasma species at the liquid surface. For treatment times >10 min, alkaline BTB solutions turned from blue to yellow due to acidic effects and also fading resulting from both decolourisation and degradation. The addition of NaN3 reduced the decolourisation rate from 99.1% without NaN3 to 68.2% and lowered the pH to 6.7. In contrast, H2O2 increased the extent of decolourisation from 60.6% to 94.0% after 5 min treatment. Additionally, an increase in decolourisation rate of the plasma treated solutions' post-discharge was observed for the first time. - Dyes and Pigments (2008)
doi:10.1016/j.dyepig.2007.03.016
http://linkinghub.elsevier.com/retrieve/pii/S0143720807000897
Outer membrane modifications of Pseudomonas fluorescens MF37 in response to hyperosmolarity.
Muriel Guyard-Nicodème, Alexis Bazire, Gaëlle Hémery, Thierry Meylheuc, Daniel Mollé, Nicole Orange, Laurène Fito-Boncompte, Marc Feuilloley, Dominique Haras, Alain Dufour, Sylvie Chevalier.
The effect of hyperosmotic condition on the outer membrane protein (Omp) composition of Pseudomonas fluorescens was investigated by proteomic analyses. The abundances of 12 proteins, including porins, lipoproteins, and the flagella subunit FliC, were modified. This was at least partly explained by altered gene expression, as shown by mRNA level study. In agreement with Omp changes, hyperosmotic condition resulted in vesicle formation and modifications of mobility and antibiotic susceptibility. - Journal of proteome research (2008) vol. 7 (3) pp. 1218-25
doi:10.1021/pr070539x
http://pubs.acs.org/doi/abs/10.1021/pr070539x
Effect of pulsed-light treatment on milk proteins and lipids.
Noura Elmnasser, Michèle Dalgalarrondo, Nicole Orange, Amina Bakhrouf, Thomas Haertlé, Michel Federighi, Jean-Marc Chobert.
Pulsed-light treatment offers the food industry a new technology for food preservation. It allows the inactivation of numerous micro-organisms including most infectious foodborne pathogens. In addition to microbial destruction, one can also question whether pulsed-light treatment induced conformational changes in food components. To investigate this question, the influence of pulsed-light treatment on protein components of milk was evaluated by using UV spectroscopy, spectrofluorometry, electrophoresis, and determination of amino acid composition. Pulsed-light treatment resulted in an increase of UV absorbance at 280 nm. The intrinsic tryptophan fluorescence of beta-lactoglobulin (BLG) showed a 7 nm red shift after 10 pulses. SDS-PAGE showed the formation of dimers after treatment of BLG by 5 pulses and more. No significant changes in the amino acid composition of proteins and lipid oxidation were observed after pulsed-light treatment. The obtained results indicated changes in the polarity of the tryptophanyl residue microenvironment of BLG solutions or changes in the tryptophan indole structure and some aggregation of studied proteins. Hence, pulsed-light treatment did not lead to very significant changes in protein components; consequently, it could be applied to process protein foods for their better preservation. - Journal of agricultural and food chemistry (2008) vol. 56 (6) pp. 1984-91
doi: 10.1021/jf0729964
http://pubs.acs.org/doi/abs/10.1021/jf0729964
Natriuretic peptides modify Pseudomonas fluorescens cytotoxicity by regulating cyclic nucleotides and modifying LPS structure.
Wilfried Veron, Nicole Orange, Marc Gj Feuilloley, Olivier Lesouhaitier.
BACKGROUND: Nervous tissues express various communication molecules including natriuretic peptides, i.e. Brain Natriuretic Peptide (BNP) and C-type Natriuretic Peptide (CNP). These molecules share structural similarities with cyclic antibacterial peptides. CNP and to a lesser extent BNP can modify the cytotoxicity of the opportunistic pathogen Pseudomonas aeruginosa. The psychrotrophic environmental species Pseudomonas fluorescens also binds to and kills neurons and glial cells, cell types that both produce natriuretic peptides. In the present study, we investigated the sensitivity of Pseudomonas fluorescens to natriuretic peptides and evaluated the distribution and variability of putative natriuretic peptide-dependent sensor systems in the Pseudomonas genus. RESULTS: Neither BNP nor CNP modified P. fluorescens MF37 growth or cultivability. However, pre-treatment of P. fluorescens MF37 with BNP or CNP provoked a decrease of the apoptotic effect of the bacterium on glial cells and an increase of its necrotic activity. By homology with eukaryotes, where natriuretic peptides act through receptors coupled to cyclases, we observed that cell-permeable stable analogues of cyclic AMP (dbcAMP) and cyclic GMP (8BcGMP) mimicked the effect of BNP and CNP on bacteria. Intra-bacterial concentrations of cAMP and cGMP were measured to study the involvement of bacterial cyclases in the regulation of P. fluorescens cytotoxicity by BNP or CNP. BNP provoked an increase (+49%) of the cAMP concentration in P. fluorescens, and CNP increased the intra-bacterial concentrations of cGMP (+136%). The effect of BNP and CNP on the virulence of P. fluorescens was independent of the potential of the bacteria to bind to glial cells. Conversely, LPS extracted from MF37 pre-treated with dbcAMP showed a higher necrotic activity than the LPS from untreated or 8BcGMP-pre-treated bacteria. Capillary electrophoresis analysis suggests that these different effects of the LPS may be due, at least in part, to variations in the structure of the macromolecule. CONCLUSION: These observations support the hypothesis that P. fluorescens responds to natriuretic peptides through a putative sensor system coupled to a cyclase that could interfere with LPS synthesis and thereby modify the overall virulence of the micro-organism. - BMC microbiology (2008) vol. 8 pp. 114
doi: 10.1186/1471-2180-8-114
http://www.biomedcentral.com/1471-2180/8/114
Non-thermal plasma technologies: new tools for bio-decontamination.
M Moreau, N Orange, M G J Feuilloley.
Bacterial control and decontamination are crucial to industrial safety assessments. However, most recently developed materials are not compatible with standard heat sterilization treatments. Advanced oxidation processes, and particularly non-thermal plasmas, are emerging and promising technologies for sanitation because they are both efficient and cheap. The applications of non-thermal plasma to bacterial control remain poorly known for several reasons: this technique was not developed for biological applications and most of the literature is in the fields of physics and chemistry. Moreover, the diversity of the devices and complexity of the plasmas made any general evaluation of the potential of the technique difficult. Finally, no experimental equipment for non-thermal plasma sterilization is commercially available and reference articles for microbiologists are rare. The present review aims to give an overview of the principles of action and applications of plasma technologies in biodecontamination. - Biotechnology advances (2008) vol. 26 (6) pp. 610-7
doi: 10.1016/j.biotechadv.2008.08.001
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4X-4T77G2W-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=888f22fe13d2d5a4840fa27a32b6a4c5
Involvement of a phospholipase C in the hemolytic activity of a clinical strain of Pseudomonas fluorescens.
Gaelle Rossignol, Annabelle Merieau, Josette Guerillon, Wilfried Veron, Olivier Lesouhaitier, Marc G J Feuilloley, Nicole Orange.
BACKGROUND: Pseudomonas fluorescens is a ubiquitous Gram-negative bacterium frequently encountered in hospitals as a contaminant of injectable material and surfaces. This psychrotrophic bacterium, commonly described as unable to grow at temperatures above 32 degrees C, is now considered non pathogenic. We studied a recently identified clinical strain of P. fluorescens biovar I, MFN1032, which is considered to cause human lung infection and can grow at 37 degrees C in laboratory conditions. RESULTS: We found that MFN1032 secreted extracellular factors with a lytic potential at least as high as that of MF37, a psychrotrophic strain of P. fluorescens or the mesophilic opportunistic pathogen, Pseudomonas aeruginosa PAO1. We demonstrated the direct, and indirect - through increases in biosurfactant release - involvement of a phospholipase C in the hemolytic activity of this bacterium. Sequence analysis assigned this phospholipase C to a new group of phospholipases C different from those produced by P. aeruginosa. We show that changes in PlcC production have pleiotropic effects and that plcC overexpression and plcC extinction increase MFN1032 toxicity and colonization, respectively. CONCLUSION: This study provides the first demonstration that a PLC is involved in the secreted hemolytic activity of a clinical strain of Pseudomonas fluorescens. Moreover, this phospholipase C seems to belong to a complex biological network associated with the biosurfactant production. - BMC microbiology (2008) vol. 8 pp. 189
doi:10.1186/1471-2180-8-189
http://www.biomedcentral.com/1471-2180/8/189
Revues sur invitation et chapitres d'ouvrages
Quorum-sensing as a target for novel biocontrol strategies directed at Pectobacterium.
Y Dessaux, A Cirou, S Uroz, X Latour, D Faure.
J Plant Pathol (2008) vol. 90 pp. 58
Control of bacterial diseases of potato caused by Pectobacterium spp. (Erwinia carotovora)
X Latour, D Faure, S Diallo, A Cirou, B Smadja, Y Dessaux, N Orange.
Cah Agric (2008) vol. 17 pp. 355-360
Quorum-sensing as a target for novel biocontrol strategies directed at Pectobacterium.
Y Dessaux, A Cirou, S Uroz, E Chapelle, X Latour, D Faure.
Biology of plant-microbe interactions (2008) vol. 6 pp. Chapter 8 : Biocontrol interactions and biotechnology. M. Lorito, S. L. Woo & F. Scala, (eds.), 1-4. APSnet, St Paul, USA
Comparative study of 7 fluorescent pseudomonad clinical isolates.
A Chapalain, G Rossignol, O Lesouhaitier, A Merieau, C Gruffaz, J Guerillon, J-M Meyer, N Orange, M G J Feuilloley.
There is some debate about the potential survival of Pseudomonas fluorescens at temperatures above 37 degrees C and its consequences for infectious potential, owing to the heterogeneity of clinical strains. Seven clinical strains growing at 37 degrees C or more were submitted for polyphasic identification; 2 were identified as Pseudomonas mosselii and 4 were precisely characterized as P. fluorescens bv. I or II. The binding indexes on glial cells of the strains identified as P. fluorescens bv. I and P. mosselii were compared with that of a reference psychrotrophic strain, P. fluorescens MF37 (bv. V). Clinical P. fluorescens had a similar adherence potential range than strain MF37. Conversely, the binding indexes for P. mosselii strains were 3 times greater than that for strain MF37. These data, and those obtained by comparing the cytotoxic activities of P. fluorescens clinical strains, suggest the existence of different virulence mechanisms, leading either to a low infectious form or to a microorganism with cytotoxic activity in the same range as that of P. mosselii or even Pseudomonas aeruginosa. - Canadian journal of microbiology (2008) vol. 54 (1) pp. 19-27
doi:10.1139/w07-110
http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=18388968&retmode=ref&cmd=prlinks
Plasmachemical decolourisation of Bromothymol Blue by gliding electric discharge at atmospheric pressure.
A Doubla, L Bouba Bello, M Fotso, J Brisset.
The colour of aqueous solutions of 3,3′-dibromothymolsulfonephtalein (Bromothymol Blue) fades when they are exposed to a gliding electric discharge, due to the nature of impinging plasma species at the liquid surface. For treatment times >10 min, alkaline BTB solutions turned from blue to yellow due to acidic effects and also fading resulting from both decolourisation and degradation. The addition of NaN3 reduced the decolourisation rate from 99.1% without NaN3 to 68.2% and lowered the pH to 6.7. In contrast, H2O2 increased the extent of decolourisation from 60.6% to 94.0% after 5 min treatment. Additionally, an increase in decolourisation rate of the plasma treated solutions' post-discharge was observed for the first time. - Dyes and Pigments (2008)
doi:10.1016/j.dyepig.2007.03.016
http://linkinghub.elsevier.com/retrieve/pii/S0143720807000897
Outer membrane modifications of Pseudomonas fluorescens MF37 in response to hyperosmolarity.
Muriel Guyard-Nicodème, Alexis Bazire, Gaëlle Hémery, Thierry Meylheuc, Daniel Mollé, Nicole Orange, Laurène Fito-Boncompte, Marc Feuilloley, Dominique Haras, Alain Dufour, Sylvie Chevalier.
The effect of hyperosmotic condition on the outer membrane protein (Omp) composition of Pseudomonas fluorescens was investigated by proteomic analyses. The abundances of 12 proteins, including porins, lipoproteins, and the flagella subunit FliC, were modified. This was at least partly explained by altered gene expression, as shown by mRNA level study. In agreement with Omp changes, hyperosmotic condition resulted in vesicle formation and modifications of mobility and antibiotic susceptibility. - Journal of proteome research (2008) vol. 7 (3) pp. 1218-25
doi:10.1021/pr070539x
http://pubs.acs.org/doi/abs/10.1021/pr070539x
Effect of pulsed-light treatment on milk proteins and lipids.
Noura Elmnasser, Michèle Dalgalarrondo, Nicole Orange, Amina Bakhrouf, Thomas Haertlé, Michel Federighi, Jean-Marc Chobert.
Pulsed-light treatment offers the food industry a new technology for food preservation. It allows the inactivation of numerous micro-organisms including most infectious foodborne pathogens. In addition to microbial destruction, one can also question whether pulsed-light treatment induced conformational changes in food components. To investigate this question, the influence of pulsed-light treatment on protein components of milk was evaluated by using UV spectroscopy, spectrofluorometry, electrophoresis, and determination of amino acid composition. Pulsed-light treatment resulted in an increase of UV absorbance at 280 nm. The intrinsic tryptophan fluorescence of beta-lactoglobulin (BLG) showed a 7 nm red shift after 10 pulses. SDS-PAGE showed the formation of dimers after treatment of BLG by 5 pulses and more. No significant changes in the amino acid composition of proteins and lipid oxidation were observed after pulsed-light treatment. The obtained results indicated changes in the polarity of the tryptophanyl residue microenvironment of BLG solutions or changes in the tryptophan indole structure and some aggregation of studied proteins. Hence, pulsed-light treatment did not lead to very significant changes in protein components; consequently, it could be applied to process protein foods for their better preservation. - Journal of agricultural and food chemistry (2008) vol. 56 (6) pp. 1984-91
doi: 10.1021/jf0729964
http://pubs.acs.org/doi/abs/10.1021/jf0729964
Natriuretic peptides modify Pseudomonas fluorescens cytotoxicity by regulating cyclic nucleotides and modifying LPS structure.
Wilfried Veron, Nicole Orange, Marc Gj Feuilloley, Olivier Lesouhaitier.
BACKGROUND: Nervous tissues express various communication molecules including natriuretic peptides, i.e. Brain Natriuretic Peptide (BNP) and C-type Natriuretic Peptide (CNP). These molecules share structural similarities with cyclic antibacterial peptides. CNP and to a lesser extent BNP can modify the cytotoxicity of the opportunistic pathogen Pseudomonas aeruginosa. The psychrotrophic environmental species Pseudomonas fluorescens also binds to and kills neurons and glial cells, cell types that both produce natriuretic peptides. In the present study, we investigated the sensitivity of Pseudomonas fluorescens to natriuretic peptides and evaluated the distribution and variability of putative natriuretic peptide-dependent sensor systems in the Pseudomonas genus. RESULTS: Neither BNP nor CNP modified P. fluorescens MF37 growth or cultivability. However, pre-treatment of P. fluorescens MF37 with BNP or CNP provoked a decrease of the apoptotic effect of the bacterium on glial cells and an increase of its necrotic activity. By homology with eukaryotes, where natriuretic peptides act through receptors coupled to cyclases, we observed that cell-permeable stable analogues of cyclic AMP (dbcAMP) and cyclic GMP (8BcGMP) mimicked the effect of BNP and CNP on bacteria. Intra-bacterial concentrations of cAMP and cGMP were measured to study the involvement of bacterial cyclases in the regulation of P. fluorescens cytotoxicity by BNP or CNP. BNP provoked an increase (+49%) of the cAMP concentration in P. fluorescens, and CNP increased the intra-bacterial concentrations of cGMP (+136%). The effect of BNP and CNP on the virulence of P. fluorescens was independent of the potential of the bacteria to bind to glial cells. Conversely, LPS extracted from MF37 pre-treated with dbcAMP showed a higher necrotic activity than the LPS from untreated or 8BcGMP-pre-treated bacteria. Capillary electrophoresis analysis suggests that these different effects of the LPS may be due, at least in part, to variations in the structure of the macromolecule. CONCLUSION: These observations support the hypothesis that P. fluorescens responds to natriuretic peptides through a putative sensor system coupled to a cyclase that could interfere with LPS synthesis and thereby modify the overall virulence of the micro-organism. - BMC microbiology (2008) vol. 8 pp. 114
doi: 10.1186/1471-2180-8-114
http://www.biomedcentral.com/1471-2180/8/114
Non-thermal plasma technologies: new tools for bio-decontamination.
M Moreau, N Orange, M G J Feuilloley.
Bacterial control and decontamination are crucial to industrial safety assessments. However, most recently developed materials are not compatible with standard heat sterilization treatments. Advanced oxidation processes, and particularly non-thermal plasmas, are emerging and promising technologies for sanitation because they are both efficient and cheap. The applications of non-thermal plasma to bacterial control remain poorly known for several reasons: this technique was not developed for biological applications and most of the literature is in the fields of physics and chemistry. Moreover, the diversity of the devices and complexity of the plasmas made any general evaluation of the potential of the technique difficult. Finally, no experimental equipment for non-thermal plasma sterilization is commercially available and reference articles for microbiologists are rare. The present review aims to give an overview of the principles of action and applications of plasma technologies in biodecontamination. - Biotechnology advances (2008) vol. 26 (6) pp. 610-7
doi: 10.1016/j.biotechadv.2008.08.001
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T4X-4T77G2W-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=888f22fe13d2d5a4840fa27a32b6a4c5
Involvement of a phospholipase C in the hemolytic activity of a clinical strain of Pseudomonas fluorescens.
Gaelle Rossignol, Annabelle Merieau, Josette Guerillon, Wilfried Veron, Olivier Lesouhaitier, Marc G J Feuilloley, Nicole Orange.
BACKGROUND: Pseudomonas fluorescens is a ubiquitous Gram-negative bacterium frequently encountered in hospitals as a contaminant of injectable material and surfaces. This psychrotrophic bacterium, commonly described as unable to grow at temperatures above 32 degrees C, is now considered non pathogenic. We studied a recently identified clinical strain of P. fluorescens biovar I, MFN1032, which is considered to cause human lung infection and can grow at 37 degrees C in laboratory conditions. RESULTS: We found that MFN1032 secreted extracellular factors with a lytic potential at least as high as that of MF37, a psychrotrophic strain of P. fluorescens or the mesophilic opportunistic pathogen, Pseudomonas aeruginosa PAO1. We demonstrated the direct, and indirect - through increases in biosurfactant release - involvement of a phospholipase C in the hemolytic activity of this bacterium. Sequence analysis assigned this phospholipase C to a new group of phospholipases C different from those produced by P. aeruginosa. We show that changes in PlcC production have pleiotropic effects and that plcC overexpression and plcC extinction increase MFN1032 toxicity and colonization, respectively. CONCLUSION: This study provides the first demonstration that a PLC is involved in the secreted hemolytic activity of a clinical strain of Pseudomonas fluorescens. Moreover, this phospholipase C seems to belong to a complex biological network associated with the biosurfactant production. - BMC microbiology (2008) vol. 8 pp. 189
doi:10.1186/1471-2180-8-189
http://www.biomedcentral.com/1471-2180/8/189
Revues sur invitation et chapitres d'ouvrages
Quorum-sensing as a target for novel biocontrol strategies directed at Pectobacterium.
Y Dessaux, A Cirou, S Uroz, X Latour, D Faure.
J Plant Pathol (2008) vol. 90 pp. 58
Control of bacterial diseases of potato caused by Pectobacterium spp. (Erwinia carotovora)
X Latour, D Faure, S Diallo, A Cirou, B Smadja, Y Dessaux, N Orange.
Cah Agric (2008) vol. 17 pp. 355-360
Quorum-sensing as a target for novel biocontrol strategies directed at Pectobacterium.
Y Dessaux, A Cirou, S Uroz, E Chapelle, X Latour, D Faure.
Biology of plant-microbe interactions (2008) vol. 6 pp. Chapter 8 : Biocontrol interactions and biotechnology. M. Lorito, S. L. Woo & F. Scala, (eds.), 1-4. APSnet, St Paul, USA
Thermoregulation of N-acyl homoserine lactone-based quorum sensing in the soft rot bacterium Pectobacterium atrosepticum.
Xavier Latour, Stéphanie Diallo, Sylvie Chevalier, Danièle Morin, Bruno Smadja, Jean-François Burini, Dominique Haras, Nicole Orange.
The psychrotolerant bacterium Pectobacterium atrosepticum produces four N-acyl homoserine lactones under a wide range of temperatures. Their thermoregulation differs from that of the exoenzyme production, described as being under quorum-sensing control. A mechanism involved in this thermoregulation consists of controlling N-acyl homoserine lactones synthase production at a transcriptional level. - Applied and environmental microbiology (2007) vol. 73 (12) pp. 4078-81
doi: 10.1128/AEM.02681-06
http://aem.asm.org/cgi/content/full/73/12/4078?view=long&pmid=17468275
Sequence diversity of the OprD protein of environmental Pseudomonas strains.
Sylvie Chevalier, Josselin Bodilis, Thomas Jaouen, Sylvie Barray, Marc G J Feuilloley, Nicole Orange.
OprD has been widely described for Pseudomonas aeruginosa at both structural and functional levels. Here, we describe the sequence diversity of the OprD proteins from other fluorescent Pseudomonads. We analysed the sequence of the oprD gene in each of the 49 Pseudomonas isolates, mostly putida and fluorescens species, obtained from various environmental sources, including soil, rhizosphere and hospitals. Phylogeny based on OprD sequences distinguished three well-separated clusters in the P. fluorescens species whereas P. putida isolates formed only one cluster. The OprD sequences were generally well conserved within each cluster whereas on the opposite, they were highly variable from one cluster to another and particularly with regards to the cluster of P. aeruginosa. Predicted secondary structures, based on the topological model elaborated for P. aeruginosa, suggest signatures in the large extracellular loops of OprD, which are linked to the OprD-based clusters. Correlations between these OprD-based clusters and ecological niches, growth on various carbon sources and antibiotic sensitivity were investigated. - Environmental microbiology (2007) vol. 9 (3) pp. 824-35
doi:10.1111/j.1462-2920.2006.01191.x
http://www3.intecrscience.wiley.com/journal/118491163/abstrat
Recurrent recovery of Pseudomonas oryzihabitans strains in a karstified chalk aquifer.
L Dussart-Baptista, J Bodilis, S Barray, N Frébourg, M Fournier, J-P Dupont, T Jouenne.
Pseudomonas oryzihabitans is an uncommon pathogen that may cause catheter-associated infections, particularly in immunocompromised patients. Although it has been isolated from environment, the source of human infection is not well documented. In the present study, 14 isolates of P. oryzihabitans were recovered over a 28-month period from a karstified chalk aquifer, allowing to advance that distributed natural water could be a source of contamination. Microbiological analyses showed that the bacterium was mainly associated with suspended particulate matters. To investigate the clonality of P. oryzihabitans environmental isolates, 16S rRNA gene sequencing, antibiogram and randomly amplified polymorphic DNA (RAPD) typings were performed. Results demonstrated (i) the presence of at least three clones within the aquifer and (ii) that the presence of the bacterium in groundwater is not only the result of a biofilm bloom but also of an exogenous contamination. - Water research (2007) vol. 41 (1) pp. 111-7
doi; 10.1016/j.watres.2006.10.007
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V73-4MBC4WX-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c1e1d7141ff706c53cd85c10562228d8
Natriuretic peptides affect Pseudomonas aeruginosa and specifically modify lipopolysaccharide biosynthesis.
Wilfried Veron, Olivier Lesouhaitier, Xaviera Pennanec, Karine Rehel, Philippe Leroux, Nicole Orange, Marc G J Feuilloley.
Natriuretic peptides of various forms are present in animals and plants, and display structural similarities to cyclic antibacterial peptides. Pretreatment of Pseudomonas aeruginosa PAO1 with brain natriuretic peptide (BNP) or C-type natriuretic peptide (CNP) increases bacterium-induced glial cell necrosis. In eukaryotes, natriuretic peptides act through receptors coupled to cyclases. We observed that stable analogs of cAMP (dibutyryl cAMP) and cGMP (8-bromo-cGMP) mimicked the effect of brain natriuretic peptide and CNP on bacteria. Further evidence for the involvement of bacterial cyclases in the regulation of P. aeruginosa PAO1 cytotoxicity by natriuretic peptides is provided by the observed doubling of intrabacterial cAMP concentration after exposure to CNP. Lipopolysaccharide (LPS) extracted from P. aeruginosa PAO1 treated with both dibutyryl cAMP and 8-bromo-cGMP induces higher levels of necrosis than LPS extracted from untreated bacteria. Capillary electrophoresis and MALDI-TOF MS analysis have shown that differences in LPS toxicity are due to specific differences in the structure of the macromolecule. Using a strain deleted in the vfr gene, we showed that the Vfr protein is essential for the effect of natriuretic peptides on P. aeruginosa PAO1 virulence. These data support the hypothesis that P. aeruginosa has a cyclic nucleotide-dependent natriuretic peptide sensor system that may affect virulence by activating the expression of Vfr and LPS biosynthesis. - The FEBS journal (2007) vol. 274 (22) pp. 5852-64
doi: 10.1111/j.1742-4658.2007.06109.x
http://www3.interscience.wiley.com/journal/118546790/abstract
Lipid composition of membranes of Escherichia coli by liquid chromatography/tandem mass spectrometry using negative electrospray ionization.
Delphine Oursel, Corinne Loutelier-Bourhis, Nicole Orange, Sylvie Chevalier, Victor Norris, Catherine M Lange.
A liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method using reversed-phase chromatography was developed for the analysis of phospholipids from bacterial extracts of a wild-type strain of Escherichia coli. Product ion mass spectra from [M--H](-) precursor ions allowed an identification of individual phospholipid species that includes both fatty acid composition and fatty acyl location on the glycerol backbone using diagnostic product ions. Thus, complete assignment, including sn-1/sn-2 fatty acyl position, was achieved for this strain of E. coli. In addition, the phospholipids were quantified relative to one another using an internal standard method. - Rapid communications in mass spectrometry : RCM (2007) vol. 21 (11) pp. 1721-8
doi: 10.1002/rcm.3013
http://www3.interscience.wiley.com/journal/114240099/abstract
Identification and relative quantification of fatty acids in Escherichia coli membranes by gas chromatography/mass spectrometry.
Delphine Oursel, Corinne Loutelier-Bourhis, Nicole Orange, Sylvie Chevalier, Victor Norris, Catherine M Lange.
The lipids that are essential to the functioning of the bacterial membrane exist in hundreds of different forms. The reasons for this diversity are far from clear but are presumably related to the roles of these lipids in both facilitating enzymic activities and generating proteolipid domains. A full understanding of bacterial physiology therefore requires characterization of lipids in different strains in a variety of environmental conditions. This characterization then becomes the basis for lipidomics, the lipid aspect of the growing field of metabolomics. To exploit the power of derivatization chemistry and of gas chromatography/mass spectrometry (GC/MS) and tandem mass spectrometry (MS/MS) for metabolomics studies, we report here the development of various GC/MS electron ionization (EI) and negative and positive chemical ionization (CI) methods for the identification and, for the first time, the relative quantification of fatty acids present in extracts from membranes of a laboratory strain of Escherichia coli. They consist of seven saturated fatty acids (C10:0, C12:0, C14:0, C15:0, C16:0, C17:0 and C18:0) and six unsaturated fatty acids (C16:1, cyC17:0 plus two isomers of C18:1, C18:2 and cyC19:0). - Rapid communications in mass spectrometry : RCM (2007) vol. 21 (20) pp. 3229-33
doi: 10.1002/rcm.3177
http://www3.interscience.wiley.com/journal/116312995/abstract
Growth temperature and OprF porin affect cell surface physicochemical properties and adhesive capacities of Pseudomonas fluorescens MF37.
Gaëlle Hemery, Sylvie Chevalier, Marie-Noëlle Bellon-Fontaine, Dominique Haras, Nicole Orange.
Pseudomonads adapt to various ecological niches by forming biofilms, which first requires bacterial adhesion on surfaces. We studied the influence of growth temperature on surface physicochemical properties of Pseudomonas fluorescens MF37 and on its adhesive capacities onto inert surfaces. It presented a global hydrophilic character, measured by microbial adhesion to solvent (MATS), and showed a cell surface more hydrophilic at 8 and 28 degrees C than at 17 degrees C. Moreover, P. fluorescens MF37 was more adhesive at 17 degrees C. This critical temperature thus should be carefully taken into account in food safety. Adhesion onto inert surfaces is thus influenced by the growth temperature, which modifies the bacteria cell wall properties through changes in the outer membrane components. Therefore, we studied the effect of the loss of OprF, the major outer membrane protein, known to act as an adhesin (root, and endothelial cells). The OprF-deficient mutant was able to adhere to surfaces, but showed the same physicochemical and adhesion properties on abiotic surfaces whatever the growth temperature. OprF is thus not essential in this adhesion process. However, we suggest that OprF is involved in the bacterial environmental temperature sensing by P. fluorescens. - Journal of industrial microbiology & biotechnology (2007) vol. 34 (1) pp. 49-54
doi; 10.1007/s10295-006-0160-x
http://www.springerlink.com/content/58441674xu78t041/
Growth promotion of quorum-quenching bacteria in the rhizosphere of Solanum tuberosum.
Amélie Cirou, Stéphanie Diallo, Caroline Kurt, Xavier Latour, Denis Faure.
Among 17 molecules structurally related to N-acylhomoserine lactone (NAHL), gamma-caprolactone (GCL), 6-caprolactone (6CL) and 4-heptanolide (HTN) were found to stimulate the degradation of NAHL by bacterial communities recovered from bulk and rhizospheric soils. In the 6CL-, GCL- and HTN-treated bacterial consortia, the NAHL-degrading bacteria were more abundant than in control (mannitol-treated) consortia. Moreover, the GCL- and HTN-consortia showed a biocontrol activity against Pectobacterium atrosepticum in soft rot assays with tubers of Solanum tuberosum. When GCL was applied to hydroponic cultures of S. tuberosum, a significant increase of the ratio of NAHL-degrading bacteria among total cultivable bacteria was observed in several independent experiments. Most of these bacteria, the growth of which was stimulated by GCL amendment, were also able to use GCL as a sole carbon source. They belong to the Rhodococcus and Delftia genera. DGGE analysis revealed that GCL treatments affected the structure of bacterial communities. This work highlights the possibility to manage the NAHL-degrading bacteria in a complex environment such as rhizosphere. - Environmental microbiology (2007) vol. 9 (6) pp. 1511-22
doi: 10.1111/j.1462-2920.2007.01270.x
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1462-2920.2007.01270.x
Gliding arc discharge in the potato pathogen Erwinia carotovora subsp. atroseptica: mechanism of lethal action and effect on membrane-associated molecules.
M Moreau, M G J Feuilloley, W Veron, T Meylheuc, S Chevalier, J-L Brisset, N Orange.
Gliding arc (glidarc) discharge is a physicochemical technique for decontamination at atmospheric pressure and ambient temperature. It leads to the destruction of bacterial phytopathogens responsible for important losses in industrial agriculture, namely, Erwinia spp., without the formation of resistant forms. We investigated the effect of a novel optimized prototype allowing bacterial killing without lag time. This prototype also decreases the required duration of treatment by 50%. The study of the time course effect of the process on bacterial morphology suggests that glidarc induces major alterations of the bacterial membrane. We showed that glidarc causes the release of bacterial genomic DNA. By contrast, an apparent decrease in the level of extractible lipopolysaccharide was observed; however, no changes in the electrophoretic pattern and cytotoxic activity of the macromolecule were noted. Analysis of extractible proteins from the outer membrane of the bacteria revealed that glidarc discharge induces the release of these proteins from the lipid environment, but may also be responsible for protein dimerization and/or aggregation. This effect was not observed in secreted enzymatic proteins, such as pectate lyase. Analysis of the data supports the hypothesis that the plasma generated by glidarc discharge is acting essentially through oxidative mechanisms. Furthermore, these results indicate that, in addition to effectively destroying bacteria, glidarc discharge should be used to improve the extraction of bacterial molecules. - Applied and environmental microbiology (2007) vol. 73 (18) pp. 5904-10
doi: 10.1128/AEM.00662-07
http://aem.asm.org/cgi/content/full/73/18/5904?view=long&pmid=17644644
Élucider le fonctionnement d'un réseau de régulation biologique par l'informatique.
G Bernot, JP Comet, J Guespin.
En modélisation mathématique, l’ordinateur effectue souvent de gros calculs de simulations. En biologie des systèmes, lorsque les interactions non linéaires rendent impossible la détermination du comportement général d’un système à partir de quelques simulations, même lorsque ce système ne contient qu’un petit nombre d’éléments, la logique formelle informatique peut assister la découverte de modèles et suggérer des expériences « à la paillasse ». - Biofutur (2007) vol. 26 (275) pp. 24-27
Assessment of faecal contamination and the relationship between pathogens and faecal bacterial indicators in an estuarine environment (Seine, France).
Aurélie Touron, Thierry Berthe, Gilles Gargala, Matthieu Fournier, Mehdy Ratajczak, Pierre Servais, Fabienne Petit.
The Seine estuary, one of the largest estuaries of the European northwest continental shelf, is subjected to numerous anthropogenic influences. Here we present an assessment of the microbial faecal contamination of the estuary water. The most vulnerable areas were defined on the basis of the fluxes of indicator organisms and the occurrence of Salmonella and Cryptosporidium sp. and Giardia sp. (oo)cysts. The microbial quality of the water changes from upstream to downstream: in the upstream area, contamination by faecal-indicator bacteria and Salmonella occurs during periods of high flow; in the urbanized area, mid-way between the uppermost areas of the estuary and its mouth, discharge from a wastewater treatment plant and a tributary degrade water quality; at the estuary mouth, the accumulation of microorganisms attached to particles in the maximum turbidity zone, particularly Clostridium perfringens spores and oocysts of Cryptosporidium, is accompanied by inputs of ThC and Escherichia coli from tributaries. In some areas, significant strong relations are observed between Salmonella, (oo)cysts of protozoan, and levels of faecal indicators. - Marine pollution bulletin (2007) vol. 54 (9) pp. 1441-50
doi: 10.1016/j.marpolbul.2007.05.009
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6N-4P5YKBF-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=4e4b3006f07d916ee6721fd3c1cd8aec
Xavier Latour, Stéphanie Diallo, Sylvie Chevalier, Danièle Morin, Bruno Smadja, Jean-François Burini, Dominique Haras, Nicole Orange.
The psychrotolerant bacterium Pectobacterium atrosepticum produces four N-acyl homoserine lactones under a wide range of temperatures. Their thermoregulation differs from that of the exoenzyme production, described as being under quorum-sensing control. A mechanism involved in this thermoregulation consists of controlling N-acyl homoserine lactones synthase production at a transcriptional level. - Applied and environmental microbiology (2007) vol. 73 (12) pp. 4078-81
doi: 10.1128/AEM.02681-06
http://aem.asm.org/cgi/content/full/73/12/4078?view=long&pmid=17468275
Sequence diversity of the OprD protein of environmental Pseudomonas strains.
Sylvie Chevalier, Josselin Bodilis, Thomas Jaouen, Sylvie Barray, Marc G J Feuilloley, Nicole Orange.
OprD has been widely described for Pseudomonas aeruginosa at both structural and functional levels. Here, we describe the sequence diversity of the OprD proteins from other fluorescent Pseudomonads. We analysed the sequence of the oprD gene in each of the 49 Pseudomonas isolates, mostly putida and fluorescens species, obtained from various environmental sources, including soil, rhizosphere and hospitals. Phylogeny based on OprD sequences distinguished three well-separated clusters in the P. fluorescens species whereas P. putida isolates formed only one cluster. The OprD sequences were generally well conserved within each cluster whereas on the opposite, they were highly variable from one cluster to another and particularly with regards to the cluster of P. aeruginosa. Predicted secondary structures, based on the topological model elaborated for P. aeruginosa, suggest signatures in the large extracellular loops of OprD, which are linked to the OprD-based clusters. Correlations between these OprD-based clusters and ecological niches, growth on various carbon sources and antibiotic sensitivity were investigated. - Environmental microbiology (2007) vol. 9 (3) pp. 824-35
doi:10.1111/j.1462-2920.2006.01191.x
http://www3.intecrscience.wiley.com/journal/118491163/abstrat
Recurrent recovery of Pseudomonas oryzihabitans strains in a karstified chalk aquifer.
L Dussart-Baptista, J Bodilis, S Barray, N Frébourg, M Fournier, J-P Dupont, T Jouenne.
Pseudomonas oryzihabitans is an uncommon pathogen that may cause catheter-associated infections, particularly in immunocompromised patients. Although it has been isolated from environment, the source of human infection is not well documented. In the present study, 14 isolates of P. oryzihabitans were recovered over a 28-month period from a karstified chalk aquifer, allowing to advance that distributed natural water could be a source of contamination. Microbiological analyses showed that the bacterium was mainly associated with suspended particulate matters. To investigate the clonality of P. oryzihabitans environmental isolates, 16S rRNA gene sequencing, antibiogram and randomly amplified polymorphic DNA (RAPD) typings were performed. Results demonstrated (i) the presence of at least three clones within the aquifer and (ii) that the presence of the bacterium in groundwater is not only the result of a biofilm bloom but also of an exogenous contamination. - Water research (2007) vol. 41 (1) pp. 111-7
doi; 10.1016/j.watres.2006.10.007
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V73-4MBC4WX-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c1e1d7141ff706c53cd85c10562228d8
Natriuretic peptides affect Pseudomonas aeruginosa and specifically modify lipopolysaccharide biosynthesis.
Wilfried Veron, Olivier Lesouhaitier, Xaviera Pennanec, Karine Rehel, Philippe Leroux, Nicole Orange, Marc G J Feuilloley.
Natriuretic peptides of various forms are present in animals and plants, and display structural similarities to cyclic antibacterial peptides. Pretreatment of Pseudomonas aeruginosa PAO1 with brain natriuretic peptide (BNP) or C-type natriuretic peptide (CNP) increases bacterium-induced glial cell necrosis. In eukaryotes, natriuretic peptides act through receptors coupled to cyclases. We observed that stable analogs of cAMP (dibutyryl cAMP) and cGMP (8-bromo-cGMP) mimicked the effect of brain natriuretic peptide and CNP on bacteria. Further evidence for the involvement of bacterial cyclases in the regulation of P. aeruginosa PAO1 cytotoxicity by natriuretic peptides is provided by the observed doubling of intrabacterial cAMP concentration after exposure to CNP. Lipopolysaccharide (LPS) extracted from P. aeruginosa PAO1 treated with both dibutyryl cAMP and 8-bromo-cGMP induces higher levels of necrosis than LPS extracted from untreated bacteria. Capillary electrophoresis and MALDI-TOF MS analysis have shown that differences in LPS toxicity are due to specific differences in the structure of the macromolecule. Using a strain deleted in the vfr gene, we showed that the Vfr protein is essential for the effect of natriuretic peptides on P. aeruginosa PAO1 virulence. These data support the hypothesis that P. aeruginosa has a cyclic nucleotide-dependent natriuretic peptide sensor system that may affect virulence by activating the expression of Vfr and LPS biosynthesis. - The FEBS journal (2007) vol. 274 (22) pp. 5852-64
doi: 10.1111/j.1742-4658.2007.06109.x
http://www3.interscience.wiley.com/journal/118546790/abstract
Lipid composition of membranes of Escherichia coli by liquid chromatography/tandem mass spectrometry using negative electrospray ionization.
Delphine Oursel, Corinne Loutelier-Bourhis, Nicole Orange, Sylvie Chevalier, Victor Norris, Catherine M Lange.
A liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) method using reversed-phase chromatography was developed for the analysis of phospholipids from bacterial extracts of a wild-type strain of Escherichia coli. Product ion mass spectra from [M--H](-) precursor ions allowed an identification of individual phospholipid species that includes both fatty acid composition and fatty acyl location on the glycerol backbone using diagnostic product ions. Thus, complete assignment, including sn-1/sn-2 fatty acyl position, was achieved for this strain of E. coli. In addition, the phospholipids were quantified relative to one another using an internal standard method. - Rapid communications in mass spectrometry : RCM (2007) vol. 21 (11) pp. 1721-8
doi: 10.1002/rcm.3013
http://www3.interscience.wiley.com/journal/114240099/abstract
Identification and relative quantification of fatty acids in Escherichia coli membranes by gas chromatography/mass spectrometry.
Delphine Oursel, Corinne Loutelier-Bourhis, Nicole Orange, Sylvie Chevalier, Victor Norris, Catherine M Lange.
The lipids that are essential to the functioning of the bacterial membrane exist in hundreds of different forms. The reasons for this diversity are far from clear but are presumably related to the roles of these lipids in both facilitating enzymic activities and generating proteolipid domains. A full understanding of bacterial physiology therefore requires characterization of lipids in different strains in a variety of environmental conditions. This characterization then becomes the basis for lipidomics, the lipid aspect of the growing field of metabolomics. To exploit the power of derivatization chemistry and of gas chromatography/mass spectrometry (GC/MS) and tandem mass spectrometry (MS/MS) for metabolomics studies, we report here the development of various GC/MS electron ionization (EI) and negative and positive chemical ionization (CI) methods for the identification and, for the first time, the relative quantification of fatty acids present in extracts from membranes of a laboratory strain of Escherichia coli. They consist of seven saturated fatty acids (C10:0, C12:0, C14:0, C15:0, C16:0, C17:0 and C18:0) and six unsaturated fatty acids (C16:1, cyC17:0 plus two isomers of C18:1, C18:2 and cyC19:0). - Rapid communications in mass spectrometry : RCM (2007) vol. 21 (20) pp. 3229-33
doi: 10.1002/rcm.3177
http://www3.interscience.wiley.com/journal/116312995/abstract
Growth temperature and OprF porin affect cell surface physicochemical properties and adhesive capacities of Pseudomonas fluorescens MF37.
Gaëlle Hemery, Sylvie Chevalier, Marie-Noëlle Bellon-Fontaine, Dominique Haras, Nicole Orange.
Pseudomonads adapt to various ecological niches by forming biofilms, which first requires bacterial adhesion on surfaces. We studied the influence of growth temperature on surface physicochemical properties of Pseudomonas fluorescens MF37 and on its adhesive capacities onto inert surfaces. It presented a global hydrophilic character, measured by microbial adhesion to solvent (MATS), and showed a cell surface more hydrophilic at 8 and 28 degrees C than at 17 degrees C. Moreover, P. fluorescens MF37 was more adhesive at 17 degrees C. This critical temperature thus should be carefully taken into account in food safety. Adhesion onto inert surfaces is thus influenced by the growth temperature, which modifies the bacteria cell wall properties through changes in the outer membrane components. Therefore, we studied the effect of the loss of OprF, the major outer membrane protein, known to act as an adhesin (root, and endothelial cells). The OprF-deficient mutant was able to adhere to surfaces, but showed the same physicochemical and adhesion properties on abiotic surfaces whatever the growth temperature. OprF is thus not essential in this adhesion process. However, we suggest that OprF is involved in the bacterial environmental temperature sensing by P. fluorescens. - Journal of industrial microbiology & biotechnology (2007) vol. 34 (1) pp. 49-54
doi; 10.1007/s10295-006-0160-x
http://www.springerlink.com/content/58441674xu78t041/
Growth promotion of quorum-quenching bacteria in the rhizosphere of Solanum tuberosum.
Amélie Cirou, Stéphanie Diallo, Caroline Kurt, Xavier Latour, Denis Faure.
Among 17 molecules structurally related to N-acylhomoserine lactone (NAHL), gamma-caprolactone (GCL), 6-caprolactone (6CL) and 4-heptanolide (HTN) were found to stimulate the degradation of NAHL by bacterial communities recovered from bulk and rhizospheric soils. In the 6CL-, GCL- and HTN-treated bacterial consortia, the NAHL-degrading bacteria were more abundant than in control (mannitol-treated) consortia. Moreover, the GCL- and HTN-consortia showed a biocontrol activity against Pectobacterium atrosepticum in soft rot assays with tubers of Solanum tuberosum. When GCL was applied to hydroponic cultures of S. tuberosum, a significant increase of the ratio of NAHL-degrading bacteria among total cultivable bacteria was observed in several independent experiments. Most of these bacteria, the growth of which was stimulated by GCL amendment, were also able to use GCL as a sole carbon source. They belong to the Rhodococcus and Delftia genera. DGGE analysis revealed that GCL treatments affected the structure of bacterial communities. This work highlights the possibility to manage the NAHL-degrading bacteria in a complex environment such as rhizosphere. - Environmental microbiology (2007) vol. 9 (6) pp. 1511-22
doi: 10.1111/j.1462-2920.2007.01270.x
http://www.blackwell-synergy.com/doi/abs/10.1111/j.1462-2920.2007.01270.x
Gliding arc discharge in the potato pathogen Erwinia carotovora subsp. atroseptica: mechanism of lethal action and effect on membrane-associated molecules.
M Moreau, M G J Feuilloley, W Veron, T Meylheuc, S Chevalier, J-L Brisset, N Orange.
Gliding arc (glidarc) discharge is a physicochemical technique for decontamination at atmospheric pressure and ambient temperature. It leads to the destruction of bacterial phytopathogens responsible for important losses in industrial agriculture, namely, Erwinia spp., without the formation of resistant forms. We investigated the effect of a novel optimized prototype allowing bacterial killing without lag time. This prototype also decreases the required duration of treatment by 50%. The study of the time course effect of the process on bacterial morphology suggests that glidarc induces major alterations of the bacterial membrane. We showed that glidarc causes the release of bacterial genomic DNA. By contrast, an apparent decrease in the level of extractible lipopolysaccharide was observed; however, no changes in the electrophoretic pattern and cytotoxic activity of the macromolecule were noted. Analysis of extractible proteins from the outer membrane of the bacteria revealed that glidarc discharge induces the release of these proteins from the lipid environment, but may also be responsible for protein dimerization and/or aggregation. This effect was not observed in secreted enzymatic proteins, such as pectate lyase. Analysis of the data supports the hypothesis that the plasma generated by glidarc discharge is acting essentially through oxidative mechanisms. Furthermore, these results indicate that, in addition to effectively destroying bacteria, glidarc discharge should be used to improve the extraction of bacterial molecules. - Applied and environmental microbiology (2007) vol. 73 (18) pp. 5904-10
doi: 10.1128/AEM.00662-07
http://aem.asm.org/cgi/content/full/73/18/5904?view=long&pmid=17644644
Élucider le fonctionnement d'un réseau de régulation biologique par l'informatique.
G Bernot, JP Comet, J Guespin.
En modélisation mathématique, l’ordinateur effectue souvent de gros calculs de simulations. En biologie des systèmes, lorsque les interactions non linéaires rendent impossible la détermination du comportement général d’un système à partir de quelques simulations, même lorsque ce système ne contient qu’un petit nombre d’éléments, la logique formelle informatique peut assister la découverte de modèles et suggérer des expériences « à la paillasse ». - Biofutur (2007) vol. 26 (275) pp. 24-27
Assessment of faecal contamination and the relationship between pathogens and faecal bacterial indicators in an estuarine environment (Seine, France).
Aurélie Touron, Thierry Berthe, Gilles Gargala, Matthieu Fournier, Mehdy Ratajczak, Pierre Servais, Fabienne Petit.
The Seine estuary, one of the largest estuaries of the European northwest continental shelf, is subjected to numerous anthropogenic influences. Here we present an assessment of the microbial faecal contamination of the estuary water. The most vulnerable areas were defined on the basis of the fluxes of indicator organisms and the occurrence of Salmonella and Cryptosporidium sp. and Giardia sp. (oo)cysts. The microbial quality of the water changes from upstream to downstream: in the upstream area, contamination by faecal-indicator bacteria and Salmonella occurs during periods of high flow; in the urbanized area, mid-way between the uppermost areas of the estuary and its mouth, discharge from a wastewater treatment plant and a tributary degrade water quality; at the estuary mouth, the accumulation of microorganisms attached to particles in the maximum turbidity zone, particularly Clostridium perfringens spores and oocysts of Cryptosporidium, is accompanied by inputs of ThC and Escherichia coli from tributaries. In some areas, significant strong relations are observed between Salmonella, (oo)cysts of protozoan, and levels of faecal indicators. - Marine pollution bulletin (2007) vol. 54 (9) pp. 1441-50
doi: 10.1016/j.marpolbul.2007.05.009
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6N-4P5YKBF-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=4e4b3006f07d916ee6721fd3c1cd8aec
OprF polymorphism as a marker of ecological niche in Pseudomonas.
Josselin Bodilis, Mickaël Hedde, Nicole Orange, Sylvie Barray.
OprF is the major outer-membrane protein of Pseudomonas sensu stricto (rRNA group I). In addition to playing a role as porin, membrane structural protein and root adhesion, this pleiotropic protein shows a length polymorphism corresponding to two types of OprF, termed OprF type 1 and OprF type 2. In a previous work, all the P. fluorescens isolated from bulk soil (non-rhizospheric) were shown to possess oprF type 1, while all the clinical P. fluorescens isolates and most rhizospheric strains corresponded to type 2. In this study, we further investigated the relation between the OprF polymorphism and the ecological niche by developing a culture-independent approach (a ratio polymerase chain reaction) to measure the percentage of each oprF type in environmental DNA samples, including two different soils and three different cultured plants (flax, wheat and grassland). Although the proportions of oprF type 2 between rhizospheric samples were quite variable, they were always very significantly higher (P<0.001) than the proportions of oprF type 2 of the adjacent bulk soil where the vast majority of oprF (>95%) corresponded to type 1. We discuss the potential applications of this ecological fingerprint in an agronomic and taxonomic point of view. - Environmental microbiology (2006) vol. 8 (9) pp. 1544-51
doi: 10.1111/j.1462-2920.2006.01045.x
http://www3.interscience.wiley.com/journal/118567478/abstract
Molecular evolution of the major outer-membrane protein gene (oprF) of Pseudomonas.
Josselin Bodilis, Sylvie Barray.
The major outer-membrane protein of Pseudomonas, OprF, is multifunctional. It is a non-specific porin that plays a role in maintenance of cell shape, in growth in a low-osmolarity environment, and in adhesion to various supports or molecules. OprF has been studied extensively for its utility as a vaccine component, its role in antimicrobial drug resistance, and its porin function. The authors have previously shown important differences between the OprF and 16S rDNA phylogenies: Pseudomonas fluorescens isolates split into two quite separate clusters, probably according to their ecological niche. In this study, the evolutionary history of the oprF gene was investigated further. The study of G+C content at the third codon position, synonymous codon usage (codon adaptation index, CAI) and genomic context showed no evidence of horizontal transfer or gene duplication. Similarly, a robust likelihood test of incongruence showed no significant incongruence between the oprF phylogeny and the species phylogeny. In addition, the ratio of nonsynonymous mutations to synonymous mutations (K(a)/K(s)) is high between the different clusters, especially between the two clusters containing P. fluorescens isolates, highlighting important modifications in evolutionary constraints during the history of the oprF gene. Since OprF is known as a pleiotropic protein, modifications in evolutionary constraints could have resulted from variations in cryptic functions, correlated with the ecological fingerprint. Finally, relaxed constraints and/or episodic positive evolution, especially for some P. fluorescens strains, could have led to a phylogeny reconstruction artifact. - Microbiology (Reading, England) (2006) vol. 152 (Pt 4) pp. 1075-88
doi: 10.1099/mic.0.28656-0
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=16549671&dopt=abstractplus
Modeling and simulation with Hybrid Functional Petri Nets of the role of interleukin-6 in human early haematopoiesis.
Sylvie Troncale, Fariza Tahi, David Campard, Jean-Pierre Vannier, J Guespin.
The regulation of human haematopoiesis is a complex biological system with numerous interdependent processes. In vivo Haematopoietic Stem Cells (HSCs) self-renew so as to maintain a constant pool of these cells. It would be very interesting to maintain these cells in vitro, in view of their therapeutical importance. Unfortunately, there is currently no known process to activate HSCs self-renewal in vitro. Since the difficulties related to in vitro experiments, modeling and simulating this process is indispensable. Moreover, the complexity of haematopoiesis makes it necessary to integrate various functionalities: both discrete and continuous models as well as consumption and production of resources. We thus focus on the use of Hybrid Functional Petri Nets, which offer a number of features and flexibility. We begin by modeling and simulating the role of a specific cytokine, interleukin-6, in the regulation of early haematopoiesis. Results obtained in silico lead to the disappearence of HSCs, which is in agreement with in vitro results. - Pacific Symposium on Biocomputing Pacific Symposium on Biocomputing (2006) pp. 427-38
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=17094258&dopt=abstractplus
Functional characterization of Pseudomonas fluorescens OprE and OprQ membrane proteins.
Thomas Jaouen, Laurent Coquet, Laure Marvin-Guy, Nicole Orange, Sylvie Chevalier, Emmanuelle Dé.
Outer membrane (OM) proteins of the OprD family may enable bacteria of the genus Pseudomonas to adapt to various environments by modulating OM permeability. The OprE and OprQ porins from P. fluorescens strain MF0 were purified and identified by MALDI-TOF mass spectrometry and N-terminal and internal microsequencing. These proteins, when reconstituted in an artificial planar lipid bilayer, induced similar ion channels with low single-conductance values. Secondary structure prediction of both proteins showed similar folding patterns into a 16 transmembrane beta-strands barrel but a highly variable amino-acid composition and length for their putative external loops implicated in porin function. Both proteins were overexpressed under poor oxygenation conditions, but not by using several amino acids as sole carbon source, indicating a different specificity for these proteins compared to the paradigm of this protein family, OprD. - Biochemical and biophysical research communications (2006) vol. 346 (3) pp. 1048-52
doi: 10.1016/j.bbrc.2006.06.013
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WBK-4K4WFG5-B&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=4163f9288246e6bc46903f22f2ceb8b5
Epigenetic acquisition of inducibility of type III cytotoxicity in P. aeruginosa.
Didier Filopon, Annabelle Mérieau, Gilles Bernot, Jean-Paul Comet, Rozenne Leberre, Benoit Guery, Benoit Polack, Janine Guespin-Michel.
BACKGROUND : Pseudomonas aeruginosa, an opportunistic pathogen, is often encountered in chronic lung diseases such as cystic fibrosis or chronic obstructive pneumonia, as well as acute settings like mechanical ventilation acquired pneumonia or neutropenic patients. It is a major cause of mortality and morbidity in these diseases. In lungs, P. aeruginosa settles in a biofilm mode of growth with the secretion of exopolysaccharides in which it is encapsulated, enhancing its antibiotic resistance and contributing to the respiratory deficiency of patients. However, bacteria must first multiply to a high density and display a cytotoxic phenotype to avoid the host's defences. A virulence determinant implicated in this step of infection is the type III secretion system (TTSS), allowing toxin injection directly into host cells. At the beginning of the infection, most strains isolated from patients' lungs possess an inducible TTSS allowing toxins injection or secretion upon in vivo or in vitro activation signals. As the infection persists most of the bacteria permanently loose this capacity, although no mutations have been evidenced. We name "non inducible" this phenotype. As suggested by the presence of a positive feedback circuit in the regulatory network controlling TTSS expression, it may be due to an epigenetic switch allowing heritable phenotypic modifications without genotype's mutations. RESULTS: Using the generalised logical method, we designed a minimal model of the TTSS regulatory network that could support the epigenetic hypothesis, and studied its dynamics which helped to define a discriminating experimental scenario sufficient to validate the epigenetic hypothesis. A mathematical framework based on formal methods from computer science allowed a rigorous validation and certification of parameters of this model leading to epigenetic behaviour. Then, we demonstrated that a non inducible strain of P. aeruginosa can stably acquire the capacity to be induced by calcium depletion for the TTSS after a short pulse of a regulatory protein. Finally, the increased cytotoxicity of a strain after this epigenetic switch was demonstrated in vivo in an acute pulmonary infection model. CONCLUSION: These results may offer new perspectives for therapeutic strategies to prevent lethal infections by P. aeruginosa by reverting the epigenetic inducibility of type III cytotoxicity. - BMC bioinformatics (2006) vol. 7 pp. 272
doi: 10.1186/1471-2105-7-272
http://www.biomedcentral.com/1471-2105/7/272
Dynamics of signals and structures.
Janine Guespin-Michel.
Comptes rendus biologies (2006) vol. 329 (12) pp. 917-8
doi: 10.1016/j.crvi.2006.08.004
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6X1F-4KWTFHH-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=fca36f45507cccbaca13b16eec4b41f6
Diversity of the dsrAB (dissimilatory sulfite reductase) gene sequences retrieved from two contrasting mudflats of the Seine estuary, France.
Julie Leloup, Laurent Quillet, Thierry Berthe, Fabienne Petit.
The diversity of sulfate-reducing microorganisms was investigated in two contrasting mudflats of the Seine estuary, by PCR amplification, cloning and sequencing of the genes coding for parts of the alpha and beta subunits of dissimilatory sulfite reductase (dsrAB). One site is located in the mixing-zone and shows marine characteristics, with high salinity and sulfate concentration, whereas the other site shows freshwater characteristics, with low salinity and sulfate concentration. Diversity and abundance of dsrAB genes differed between the two sites. In the mixing-zone sediments, most of the dsrAB sequences were affiliated to those of marine Gram-negative bacteria belonging to the order of Desulfobacterales, whereas in the freshwater sediments, a majority of dsrAB sequences was related to those of the Gram-positive bacteria belonging to the genus Desulfotomaculum. It is speculated that this is related to the salinity and the sulfate concentration in the two mudflats. - FEMS microbiology ecology (2006) vol. 55 (2) pp. 230-8
doi: 10.1111/j.1574-6941.2005.00021.x
http://www3.interscience.wiley.com/journal/118595919/abstract
Josselin Bodilis, Mickaël Hedde, Nicole Orange, Sylvie Barray.
OprF is the major outer-membrane protein of Pseudomonas sensu stricto (rRNA group I). In addition to playing a role as porin, membrane structural protein and root adhesion, this pleiotropic protein shows a length polymorphism corresponding to two types of OprF, termed OprF type 1 and OprF type 2. In a previous work, all the P. fluorescens isolated from bulk soil (non-rhizospheric) were shown to possess oprF type 1, while all the clinical P. fluorescens isolates and most rhizospheric strains corresponded to type 2. In this study, we further investigated the relation between the OprF polymorphism and the ecological niche by developing a culture-independent approach (a ratio polymerase chain reaction) to measure the percentage of each oprF type in environmental DNA samples, including two different soils and three different cultured plants (flax, wheat and grassland). Although the proportions of oprF type 2 between rhizospheric samples were quite variable, they were always very significantly higher (P<0.001) than the proportions of oprF type 2 of the adjacent bulk soil where the vast majority of oprF (>95%) corresponded to type 1. We discuss the potential applications of this ecological fingerprint in an agronomic and taxonomic point of view. - Environmental microbiology (2006) vol. 8 (9) pp. 1544-51
doi: 10.1111/j.1462-2920.2006.01045.x
http://www3.interscience.wiley.com/journal/118567478/abstract
Molecular evolution of the major outer-membrane protein gene (oprF) of Pseudomonas.
Josselin Bodilis, Sylvie Barray.
The major outer-membrane protein of Pseudomonas, OprF, is multifunctional. It is a non-specific porin that plays a role in maintenance of cell shape, in growth in a low-osmolarity environment, and in adhesion to various supports or molecules. OprF has been studied extensively for its utility as a vaccine component, its role in antimicrobial drug resistance, and its porin function. The authors have previously shown important differences between the OprF and 16S rDNA phylogenies: Pseudomonas fluorescens isolates split into two quite separate clusters, probably according to their ecological niche. In this study, the evolutionary history of the oprF gene was investigated further. The study of G+C content at the third codon position, synonymous codon usage (codon adaptation index, CAI) and genomic context showed no evidence of horizontal transfer or gene duplication. Similarly, a robust likelihood test of incongruence showed no significant incongruence between the oprF phylogeny and the species phylogeny. In addition, the ratio of nonsynonymous mutations to synonymous mutations (K(a)/K(s)) is high between the different clusters, especially between the two clusters containing P. fluorescens isolates, highlighting important modifications in evolutionary constraints during the history of the oprF gene. Since OprF is known as a pleiotropic protein, modifications in evolutionary constraints could have resulted from variations in cryptic functions, correlated with the ecological fingerprint. Finally, relaxed constraints and/or episodic positive evolution, especially for some P. fluorescens strains, could have led to a phylogeny reconstruction artifact. - Microbiology (Reading, England) (2006) vol. 152 (Pt 4) pp. 1075-88
doi: 10.1099/mic.0.28656-0
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=16549671&dopt=abstractplus
Modeling and simulation with Hybrid Functional Petri Nets of the role of interleukin-6 in human early haematopoiesis.
Sylvie Troncale, Fariza Tahi, David Campard, Jean-Pierre Vannier, J Guespin.
The regulation of human haematopoiesis is a complex biological system with numerous interdependent processes. In vivo Haematopoietic Stem Cells (HSCs) self-renew so as to maintain a constant pool of these cells. It would be very interesting to maintain these cells in vitro, in view of their therapeutical importance. Unfortunately, there is currently no known process to activate HSCs self-renewal in vitro. Since the difficulties related to in vitro experiments, modeling and simulating this process is indispensable. Moreover, the complexity of haematopoiesis makes it necessary to integrate various functionalities: both discrete and continuous models as well as consumption and production of resources. We thus focus on the use of Hybrid Functional Petri Nets, which offer a number of features and flexibility. We begin by modeling and simulating the role of a specific cytokine, interleukin-6, in the regulation of early haematopoiesis. Results obtained in silico lead to the disappearence of HSCs, which is in agreement with in vitro results. - Pacific Symposium on Biocomputing Pacific Symposium on Biocomputing (2006) pp. 427-38
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=17094258&dopt=abstractplus
Functional characterization of Pseudomonas fluorescens OprE and OprQ membrane proteins.
Thomas Jaouen, Laurent Coquet, Laure Marvin-Guy, Nicole Orange, Sylvie Chevalier, Emmanuelle Dé.
Outer membrane (OM) proteins of the OprD family may enable bacteria of the genus Pseudomonas to adapt to various environments by modulating OM permeability. The OprE and OprQ porins from P. fluorescens strain MF0 were purified and identified by MALDI-TOF mass spectrometry and N-terminal and internal microsequencing. These proteins, when reconstituted in an artificial planar lipid bilayer, induced similar ion channels with low single-conductance values. Secondary structure prediction of both proteins showed similar folding patterns into a 16 transmembrane beta-strands barrel but a highly variable amino-acid composition and length for their putative external loops implicated in porin function. Both proteins were overexpressed under poor oxygenation conditions, but not by using several amino acids as sole carbon source, indicating a different specificity for these proteins compared to the paradigm of this protein family, OprD. - Biochemical and biophysical research communications (2006) vol. 346 (3) pp. 1048-52
doi: 10.1016/j.bbrc.2006.06.013
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WBK-4K4WFG5-B&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=4163f9288246e6bc46903f22f2ceb8b5
Epigenetic acquisition of inducibility of type III cytotoxicity in P. aeruginosa.
Didier Filopon, Annabelle Mérieau, Gilles Bernot, Jean-Paul Comet, Rozenne Leberre, Benoit Guery, Benoit Polack, Janine Guespin-Michel.
BACKGROUND : Pseudomonas aeruginosa, an opportunistic pathogen, is often encountered in chronic lung diseases such as cystic fibrosis or chronic obstructive pneumonia, as well as acute settings like mechanical ventilation acquired pneumonia or neutropenic patients. It is a major cause of mortality and morbidity in these diseases. In lungs, P. aeruginosa settles in a biofilm mode of growth with the secretion of exopolysaccharides in which it is encapsulated, enhancing its antibiotic resistance and contributing to the respiratory deficiency of patients. However, bacteria must first multiply to a high density and display a cytotoxic phenotype to avoid the host's defences. A virulence determinant implicated in this step of infection is the type III secretion system (TTSS), allowing toxin injection directly into host cells. At the beginning of the infection, most strains isolated from patients' lungs possess an inducible TTSS allowing toxins injection or secretion upon in vivo or in vitro activation signals. As the infection persists most of the bacteria permanently loose this capacity, although no mutations have been evidenced. We name "non inducible" this phenotype. As suggested by the presence of a positive feedback circuit in the regulatory network controlling TTSS expression, it may be due to an epigenetic switch allowing heritable phenotypic modifications without genotype's mutations. RESULTS: Using the generalised logical method, we designed a minimal model of the TTSS regulatory network that could support the epigenetic hypothesis, and studied its dynamics which helped to define a discriminating experimental scenario sufficient to validate the epigenetic hypothesis. A mathematical framework based on formal methods from computer science allowed a rigorous validation and certification of parameters of this model leading to epigenetic behaviour. Then, we demonstrated that a non inducible strain of P. aeruginosa can stably acquire the capacity to be induced by calcium depletion for the TTSS after a short pulse of a regulatory protein. Finally, the increased cytotoxicity of a strain after this epigenetic switch was demonstrated in vivo in an acute pulmonary infection model. CONCLUSION: These results may offer new perspectives for therapeutic strategies to prevent lethal infections by P. aeruginosa by reverting the epigenetic inducibility of type III cytotoxicity. - BMC bioinformatics (2006) vol. 7 pp. 272
doi: 10.1186/1471-2105-7-272
http://www.biomedcentral.com/1471-2105/7/272
Dynamics of signals and structures.
Janine Guespin-Michel.
Comptes rendus biologies (2006) vol. 329 (12) pp. 917-8
doi: 10.1016/j.crvi.2006.08.004
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6X1F-4KWTFHH-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=fca36f45507cccbaca13b16eec4b41f6
Diversity of the dsrAB (dissimilatory sulfite reductase) gene sequences retrieved from two contrasting mudflats of the Seine estuary, France.
Julie Leloup, Laurent Quillet, Thierry Berthe, Fabienne Petit.
The diversity of sulfate-reducing microorganisms was investigated in two contrasting mudflats of the Seine estuary, by PCR amplification, cloning and sequencing of the genes coding for parts of the alpha and beta subunits of dissimilatory sulfite reductase (dsrAB). One site is located in the mixing-zone and shows marine characteristics, with high salinity and sulfate concentration, whereas the other site shows freshwater characteristics, with low salinity and sulfate concentration. Diversity and abundance of dsrAB genes differed between the two sites. In the mixing-zone sediments, most of the dsrAB sequences were affiliated to those of marine Gram-negative bacteria belonging to the order of Desulfobacterales, whereas in the freshwater sediments, a majority of dsrAB sequences was related to those of the Gram-positive bacteria belonging to the genus Desulfotomaculum. It is speculated that this is related to the salinity and the sulfate concentration in the two mudflats. - FEMS microbiology ecology (2006) vol. 55 (2) pp. 230-8
doi: 10.1111/j.1574-6941.2005.00021.x
http://www3.interscience.wiley.com/journal/118595919/abstract
Lethal effect of the gliding arc discharges on Erwinia spp.
M Moreau, M G J Feuilloley, N Orange, J-L Brisset.
AIMS: To compare the decontamination performances of glidarc on strains of Erwinia of industrial interest. METHODS AND RESULTS: Cultures of Erwinia carotovora carotovora, Erwinia carotovora atroseptica and Erwinia chrysanthemi taken in stationary phase were exposed to the plasma generated by electric discharges in a gliding arc reactor prototype. The kinetics of destruction of bacteria were followed by direct platting. All bacterial strains presented a three-phase destruction kinetics leading to an apparent sterilization within 10 min. Epifluorescent observations using life/dead probes revealed the absence of viable but not cultivable resistant forms. Measurement of the physical parameters of the medium confirmed that the technique was nonthermal but that reactive species responsible for a decrease of the pH were generated. However, even after neutralization the medium did not allow bacterial growth. CONCLUSIONS: The results demonstrate that glidarc allows a rapid and complete destruction of planctonic strains of Erwinias without formation of resistant forms. SIGNIFICANCE AND IMPACT OF THE STUDY: The reduction rate obtained by this technique shows the great industrial interest of glidarc for decontamination and suggests that it can be used for sterilization of industrial water effluents. - Journal of applied microbiology (2005) vol. 98 (5) pp. 1039-46
doi: 10.1111/j.1365-2672.2004.02535.x
http://www3.interscience.wiley.com/journal/118711293/abstract
Dynamics of sulfate-reducing microorganisms (dsrAB genes) in two contrasting mudflats of the Seine estuary (France).
J Leloup, F Petit, D Boust, J Deloffre, G Bally, O Clarisse, L Quillet.
By combining molecular biology and biochemical approaches, the dynamics of sulfate-reducing microorganisms (SRM) was investigated in the sediments of the Seine estuary (France). Both intertidal mixing-zone and freshwater mudflats were sampled during a 1-year period; the quantification of SRM was realized by using competitive polymerase chain reaction (PCR) based on dsrAB gene amplification, previously described by Leloup et al. (2004), and sulfate reduction rate (SRR) was determined via the SO4(2-) radiotracer method. Throughout the year, abundance of dsrAB genes and SRR were predominantly high in the top 15 cm of the sediment. A seasonal dynamic was observed; a predominance of activity was noted during the early summer, and seems to be mainly controlled by physical-chemical parameters (temperature and dissolved organic carbon concentration) and topographic evolution of the mudflat (erosion/deposit erosion). - Microbial ecology (2005) vol. 50 (3) pp. 307-14
doi:10.1007/s00248-004-0034-6
http://www.springerlink.com/content/763q5g74132530gp/
Detection of Salmonella in environmental water and sediment by a nested-multiplex polymerase chain reaction assay.
Aurélie Touron, Thierry Berthe, Barbara Pawlak, Fabienne Petit.
From 1995 to 2002, 53 serovars of Salmonella were isolated in the Seine estuary (France). The 3 serovars most frequently found were S. enterica serovar Typhimurium, S. enterica serovar Infantis and S. enterica serovar Virchow. A nested multiplex PCR (nm-PCR) assay was developed to detect the presence of Salmonella in estuarine water and sediment samples. The target gene used was the phase 1 flagellin fliC chromosomal gene, present in all Salmonella serovars. A set of 4 primers was first used to amplify an 890-bp sequence of the fliC gene, and then a second set of 3 primers was used for the nested PCR. The nmPCR method has been successfully tested for 28 serovars, 13 of which are of epidemiological significance. The detection limit of the assay, without any pre-enrichment step, was estimated at 1 CFU in deionized water, and at 4-5 CFU in the reaction mixture when tested on estuarine water seeded with a Salmonella strain. When the nmPCR was used together with the classical culture method in environmental samples, it gave additional positive results for 11.3% of the sediment samples and 20% of the water samples despite a high background of other bacteria. Overall, the results demonstrated that this molecular approach informed us about the contamination by Salmonella of estuarine water and sediment samples. Positive amplifications suggested the presence of Salmonella DNA and could thus provide information about a recent (culturable) or past (non-culturable, released DNA) contamination of environmental samples by this pathogenic bacteria. - Research in microbiology (2005) vol. 156 (4) pp. 541-53
doi: 10.1016/j.resmic.2005.01.001
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-4FBW3PN-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c210a0af68729e0cb861fe416595a9e5
Bistability and hysteresis in epigenetic regulation of the lactose operon. Since Delbrück, a long series of ignored models.
M Laurent, G Charvin, J Guespin-Michel.
Bistability is the capacity of a system to switch in an "all-or-none" manner between alternative steady states. This powerful concept originates from the analysis of non-linear equations driving open systems. It is one of the various patterns of regulation associated with a particular class of dynamic structures that Glansdorff and Prigogine baptised "dissipative structures". The idea of discontinuous transitions between alternative states was first formulated much earlier, by Delbrück, in 1949. Cohn and Horibata and Novick and Weiner confirmed that such transitions occur in experiments on the lactose operon carried out ten years later. Modelling with non-linear differential equations made it possible to simulate the dynamic behaviour of the lac operon, and modelling by asynchronous logical analysis elucidated the determinant role played by positive feedback circuits in the emergence of multistationarity. Nevertheless, these studies were largely ignored until the recent demonstration of the hysteretic nature of the bistable transition between alternative states of the lac operon. As originally suggested by Delbrück, the pattern of lactose consumption adopted by the bacterium is controlled epigenetically rather than genetically: the true key determinant is the direction of change of an environmental variable with respect to the structural components of the operon. - Cellular and molecular biology (Noisy-le-Grand, France) (2005) vol. 51 (7) pp. 583-94
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=16359608&dopt=abstractplus
M Moreau, M G J Feuilloley, N Orange, J-L Brisset.
AIMS: To compare the decontamination performances of glidarc on strains of Erwinia of industrial interest. METHODS AND RESULTS: Cultures of Erwinia carotovora carotovora, Erwinia carotovora atroseptica and Erwinia chrysanthemi taken in stationary phase were exposed to the plasma generated by electric discharges in a gliding arc reactor prototype. The kinetics of destruction of bacteria were followed by direct platting. All bacterial strains presented a three-phase destruction kinetics leading to an apparent sterilization within 10 min. Epifluorescent observations using life/dead probes revealed the absence of viable but not cultivable resistant forms. Measurement of the physical parameters of the medium confirmed that the technique was nonthermal but that reactive species responsible for a decrease of the pH were generated. However, even after neutralization the medium did not allow bacterial growth. CONCLUSIONS: The results demonstrate that glidarc allows a rapid and complete destruction of planctonic strains of Erwinias without formation of resistant forms. SIGNIFICANCE AND IMPACT OF THE STUDY: The reduction rate obtained by this technique shows the great industrial interest of glidarc for decontamination and suggests that it can be used for sterilization of industrial water effluents. - Journal of applied microbiology (2005) vol. 98 (5) pp. 1039-46
doi: 10.1111/j.1365-2672.2004.02535.x
http://www3.interscience.wiley.com/journal/118711293/abstract
Dynamics of sulfate-reducing microorganisms (dsrAB genes) in two contrasting mudflats of the Seine estuary (France).
J Leloup, F Petit, D Boust, J Deloffre, G Bally, O Clarisse, L Quillet.
By combining molecular biology and biochemical approaches, the dynamics of sulfate-reducing microorganisms (SRM) was investigated in the sediments of the Seine estuary (France). Both intertidal mixing-zone and freshwater mudflats were sampled during a 1-year period; the quantification of SRM was realized by using competitive polymerase chain reaction (PCR) based on dsrAB gene amplification, previously described by Leloup et al. (2004), and sulfate reduction rate (SRR) was determined via the SO4(2-) radiotracer method. Throughout the year, abundance of dsrAB genes and SRR were predominantly high in the top 15 cm of the sediment. A seasonal dynamic was observed; a predominance of activity was noted during the early summer, and seems to be mainly controlled by physical-chemical parameters (temperature and dissolved organic carbon concentration) and topographic evolution of the mudflat (erosion/deposit erosion). - Microbial ecology (2005) vol. 50 (3) pp. 307-14
doi:10.1007/s00248-004-0034-6
http://www.springerlink.com/content/763q5g74132530gp/
Detection of Salmonella in environmental water and sediment by a nested-multiplex polymerase chain reaction assay.
Aurélie Touron, Thierry Berthe, Barbara Pawlak, Fabienne Petit.
From 1995 to 2002, 53 serovars of Salmonella were isolated in the Seine estuary (France). The 3 serovars most frequently found were S. enterica serovar Typhimurium, S. enterica serovar Infantis and S. enterica serovar Virchow. A nested multiplex PCR (nm-PCR) assay was developed to detect the presence of Salmonella in estuarine water and sediment samples. The target gene used was the phase 1 flagellin fliC chromosomal gene, present in all Salmonella serovars. A set of 4 primers was first used to amplify an 890-bp sequence of the fliC gene, and then a second set of 3 primers was used for the nested PCR. The nmPCR method has been successfully tested for 28 serovars, 13 of which are of epidemiological significance. The detection limit of the assay, without any pre-enrichment step, was estimated at 1 CFU in deionized water, and at 4-5 CFU in the reaction mixture when tested on estuarine water seeded with a Salmonella strain. When the nmPCR was used together with the classical culture method in environmental samples, it gave additional positive results for 11.3% of the sediment samples and 20% of the water samples despite a high background of other bacteria. Overall, the results demonstrated that this molecular approach informed us about the contamination by Salmonella of estuarine water and sediment samples. Positive amplifications suggested the presence of Salmonella DNA and could thus provide information about a recent (culturable) or past (non-culturable, released DNA) contamination of environmental samples by this pathogenic bacteria. - Research in microbiology (2005) vol. 156 (4) pp. 541-53
doi: 10.1016/j.resmic.2005.01.001
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-4FBW3PN-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c210a0af68729e0cb861fe416595a9e5
Bistability and hysteresis in epigenetic regulation of the lactose operon. Since Delbrück, a long series of ignored models.
M Laurent, G Charvin, J Guespin-Michel.
Bistability is the capacity of a system to switch in an "all-or-none" manner between alternative steady states. This powerful concept originates from the analysis of non-linear equations driving open systems. It is one of the various patterns of regulation associated with a particular class of dynamic structures that Glansdorff and Prigogine baptised "dissipative structures". The idea of discontinuous transitions between alternative states was first formulated much earlier, by Delbrück, in 1949. Cohn and Horibata and Novick and Weiner confirmed that such transitions occur in experiments on the lactose operon carried out ten years later. Modelling with non-linear differential equations made it possible to simulate the dynamic behaviour of the lac operon, and modelling by asynchronous logical analysis elucidated the determinant role played by positive feedback circuits in the emergence of multistationarity. Nevertheless, these studies were largely ignored until the recent demonstration of the hysteretic nature of the bistable transition between alternative states of the lac operon. As originally suggested by Delbrück, the pattern of lactose consumption adopted by the bacterium is controlled epigenetically rather than genetically: the true key determinant is the direction of change of an environmental variable with respect to the structural components of the operon. - Cellular and molecular biology (Noisy-le-Grand, France) (2005) vol. 51 (7) pp. 583-94
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=16359608&dopt=abstractplus
Thermodependence of growth and enzymatic activities implicated in pathogenicity of two Erwinia carotovora subspecies (Pectobacterium spp.).
Bruno Smadja, Xavier Latour, Sameh Trigui, Jean François Burini, Sylvie Chevalier, Nicole Orange.
Erwinia carotovora subsp. atroseptica and Erwinia carotovora subsp. carotovora can cause substantial damage to economically important plant crops and stored products. The occurrence of the disease and the scale of the damage are temperature dependent. Disease development consists first of active multiplication of the bacteria in the infection area and then production of numerous extracellular enzymes. We investigated the effects of various temperatures on these two steps. We assayed the specific growth rate and the pectate lyase and protease activities for eight strains belonging to E. carotovora subsp. atroseptica and E. carotovora subsp. carotovora in vitro. The temperature effect on growth rate and on pectate lyase activity is different for the two subspecies, but protease activity appears to be similarly thermoregulated. Our results are in agreement with ecological data implicating E. carotovora subsp. atroseptica in disease when the temperature is below 20 degrees C. The optimal temperature for pathogenicity appears to be different from the optimal growth temperature but seems to be a compromise between this temperature and temperatures at which lytic activities are maximal. - Canadian journal of microbiology (2004) vol. 50 (1) pp. 19-27
doi: 10.1139/w03-099
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=15052318&dopt=abstractplus
Regulation of the cytotoxic effects of Pseudomonas fluorescens by growth temperature.
Laurent Picot, Sana Mezghani-Abdelmoula, Sylvie Chevalier, Annabelle Merieau, Olivier Lesouhaitier, Josette Guerillon, Lionel Cazin, Nicole Orange, Marc G J Feuilloley.
We had previously shown that the psychrotrophic bacterium Pseudomonas fluorescens can act as a pathogen, inducing apoptosis and necrosis in neurons and glial cells. In the present study, we investigated the influence of the growth temperature of P. fluorescens on its infectious potential. Adherence of P. fluorescens to glial cells was found to be maximal with bacteria grown at a low temperature (8 degrees C). At that temperature the swimming behaviour was markedly reduced. An increase in the growth temperature to 19, 28 or 32 degrees C strongly diminished the binding of bacteria to host cells. Thus, the adhesion phenotype of P. fluorescens appears to be independent of the motility of the bacteria. The apoptotic effect of P. fluorescens, determined by morphological (nuclear condensation) and biochemical (induction of nitric oxide synthase activity) indicators, correlated well with its binding activity on glial cells. In contrast, there was a clear dissociation between maximum binding and maximal necrotic action (measured by the release of lactate dehydrogenase) observed with bacteria grown at 19 degrees C. As suggested by capillary electrophoresis analysis, the differences in apoptotic effects may be related to variations in the molecular structure of LPS originating from bacteria grown at low and high temperatures, whereas the necrotic effect, which was maximal at the optimum temperature for the secretion of exoenzymes, could reflect variations in the metabolic activity of bacteria. - Research in microbiology (2004) vol. 155 (1) pp. 39-46
doi: 10.1016/j.resmic.2003.09.014
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-49VC608-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9934e66528de4664f3be764e5cd7483f
Pore size dependence on growth temperature is a common characteristic of the major outer membrane protein OprF in psychrotrophic and mesophilic Pseudomonas species.
Thomas Jaouen, Emmanuelle Dé, Sylvie Chevalier, Nicole Orange.
Pseudomonas species adapt well to hostile environments, which are often subjected to rapid variations. In these bacteria, the outer membrane plays an important role in the sensing of environmental conditions such as temperature. In previous studies, it has been shown that in the psychrotrophic strain P. fluorescens MF0, the major porin OprF changes its channel size according to the growth conditions and could affect outer membrane permeability. Studies of the channel-forming properties of OprFs from P. putida 01G3 and P. aeruginosa PAO1 in planar lipid bilayers generated similar results. The presence of a cysteine- or proline-rich cluster in the central linker region is not essential for channel size modulations. These findings suggest that OprF could adopt two alternative conformations in the outer membrane and that folding is thermoregulated. In contrast, no difference according to growth temperature was observed for structurally different outer membrane proteins, such as OprE3 from the Pseudomonas OprD family of specific porins. Our results are consistent with the fact that the decrease in channel size observed at low growth temperature is a particular feature of the OprF porin in various psychrotrophic and mesophilic Pseudomonas species isolated from diverse ecological niches. The ability to reduce outer membrane permeability at low growth temperature could provide these bacteria with adaptive advantages. - Applied and environmental microbiology (2004) vol. 70 (11) pp. 6665-9
doi: 10.1128/AEM.70.11.6665-6669.2004
http://aem.asm.org/cgi/content/full/70/11/6665?view=long&pmid=15528532
Phylogenetic relationships between environmental and clinical isolates of Pseudomonas fluorescens and related species deduced from 16S rRNA gene and OprF protein sequences.
Josselin Bodilis, Raphaël Calbrix, Josette Guérillon, Annabelle Mérieau, Barbara Pawlak, Nicole Orange, Sylvie Barray.
The major surface protein of the genus Pseudomonas, OprF, is a non-specific porin that plays an important role in maintenance of cell shape, in growth in a low osmolarity environment, and in adhesion to various supports. The objectives of our study were (i) to carry out a comparative analysis of phylogenies obtained from the OprF protein and from the 16S rRNA gene in 41 isolates from various sources (water, soil, milk and the hospital) and (ii) to investigate the physiological characteristics correlated with the phylogeny of OprF. We report here an important incongruence between the phylogenies of the 16S rRNA gene and the OprF protein. Phylogenetic analysis of 16S rRNA genes grouped Pseudomonas fluorescens isolates into one cluster (termed fluorescens r-cluster) whilst the phylogeny of the OprF protein divided Pseudomonas fluorescens isolates into two quite distinct clusters (termed fluorescens 1 o-cluster and fluorescens 2 o-cluster) that may be related to the original habitat of the strain. The fluorescens 1 o-cluster contained the majority of non-rhizospheric soil isolates, while the fluorescens 2 o-cluster contained all our clinical isolates and most of the rhizospheric isolates (which are fixed to the roots). In order to check this correlation, we studied two physiological characteristics: the range of growth temperature and the capacity for non-specific adhesion to polystyrene. The temperature range study for strains did not explain the existence of the two o-clusters but it did confirm the capacity of certain P. fluorescens strains to grow at 37 degrees C. The adhesion capacities of the isolates in the two o-clusters seems to be correlated with ecological niche. - Systematic and applied microbiology (2004) vol. 27 (1) pp. 93-108
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=15053326&dopt=abstractplus
Modelling and simulating biological processes in the genomic era: an account of a multidisciplinary thematic school held in Evry (France) in April 2004.
F Képès, P Amar, G Barlovatz, G Bernot, C Froidevaux, JL Giavitto, J Guespin, F Molina, V Norris, V Schächter, P Tracqui.
J. Biol. Phys. Chem. (2004) vol. 4 pp. 131–136
Les réseaux de régulation biologique : rencontre entre biologie et informatique : Production de mucus chez P. aeruginosa = The network of biological regulation: encounter between biology and computer science: mucus production in P. aeruginosa.
J Guespin, G Bernot, J Comet.
TSI. Technique et science informatiques (2004) vol. 23 (7) pp. 939-945
http://cat.inist.fr/?aModele=afficheN&cpsidt=16512123
Involvement of N-acylhomoserine lactones throughout plant infection by Erwinia carotovora subsp. atroseptica (Pectobacterium atrosepticum).
Bruno Smadja, Xavier Latour, Denis Faure, Sylvie Chevalier, Yves Dessaux, Nicole Orange.
Erwinia carotovora subsp. atroseptica is responsible for potato blackleg disease in the field and tuber soft rot during crop storage. The process leading to the disease occurs in two phases: a primary invasion step followed by a maceration step. Bacteria-to-bacteria communication is associated with a quorum-sensing (QS) process based on the production of N-acylhomoserine lactones (HSL). The role of HSL throughout plant infection was analyzed. To this purpose, HSL produced by a specific E. carotovora subsp. atroseptica wild-type strain, which was particularly virulent on potato, were identified. A derivative of this strain that expressed an HSL lactonase gene and produced low amounts of HSL was generated. The comparison of these strains allowed the evaluation of the role of HSL and QS in disease establishment and development. Bacterial growth and motility; activity of proteins secreted by type I, II, and III systems; and hypersensitive and maceration reactions were evaluated. Results indicated that HSL production and QS regulate only those traits involved in the second stage of the host plant infection (i.e., tissue maceration) and hypersensitive response in nonhost tobacco plants. Therefore, the use of QS quenching strategies for biological control in E. carotovora subsp. atroseptica cannot prevent initial infection and multiplication of this pathogen. - Molecular plant-microbe interactions : MPMI (2004) vol. 17 (11) pp. 1269-78
doi: 10.1094/MPMI.2004.17.11.1269
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=15553252&dopt=abstractplus
Epigenesis and dynamic similarity in two regulatory networks in Pseudomonas aeruginosa.
Janine F Guespin-Michel, Gilles Bernot, Jean Paul Comet, Annabelle Mérieau, Adrien Richard, Christian Hulen, Benoit Polack.
Mucoidy and cytotoxicity arise from two independent modifications of the phenotype of the bacterium Pseudomonas aeruginosa that contribute to the mortality and morbidity of cystic fibrosis. We show that, even though the transcriptional regulatory networks controlling both processes are quite different from a molecular or mechanistic point of view, they may be identical from a dynamic point of view: epigenesis may in both cases be the cause of the acquisition of these new phenotypes. This was highlighted by the identity of formal graphs modelling these networks. A mathematical framework based on formal methods from computer science was defined and implemented with a software environment. It allows an easy and rigorous validation and certification of these models and of the experimental methods that can be proposed to falsify or validate the underlying hypothesis. - Acta biotheoretica (2004) vol. 52 (4) pp. 379-90
doi:10.1023/B:ACBI.0000046604.18092.a7
http://www.springerlink.com/content/l701x187324r51uu/
Application of formal methods to biological regulatory networks: extending Thomas' asynchronous logical approach with temporal logic.
Gilles Bernot, Jean-Paul Comet, Adrien Richard, Janine Guespin.
Based on the discrete definition of biological regulatory networks developed by René Thomas, we provide a computer science formal approach to treat temporal properties of biological regulatory networks, expressed in computational tree logic. It is then possible to build all the models satisfying a set of given temporal properties. Our approach is illustrated with the mucus production in Pseudomonas aeruginosa. This application of formal methods from computer science to biological regulatory networks should open the way to many other fruitful applications. - Journal of theoretical biology (2004) vol. 229 (3) pp. 339-47
doi: 10.1016/j.jtbi.2004.04.003
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WMD-4CGM88S-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ba6b5152987921c37e5ff30be9408c7f
A logical (discrete) formulation for the storage and recall of environmental signals in plants.
M Thellier, J Demongeot, V Norris, J Guespin, C Ripoll, R Thomas.
When subjected to an appropriate asymmetric stimulus, seedlings of Bidens pilosa L. "store" a symmetry-breaking instruction that will finally take effect (in the form of a differential growth of the cotyledonary buds) only if the plants are in a state in which they can "recall" this information. The ability of the plants to recall the stored symmetry-breaking instruction may be switched "on" or "off" by the application of a variety of stimuli. Although its detailed phenomenology is rather complicated, the overall behaviour of the plant storage/recall system can be modelled by use of an asynchronous, logical (discrete) description involving positive and negative feedback circuits, which are required for the existence of multi-stationarity and stability, respectively. The state tables, as used in this formalism, give a concise and easy-to-handle description of the evolution of the system and make it particularly easy to determine its stable states. This modelling approach may be extended to the formulation of many other experimental systems. - Plant biology (Stuttgart, Germany) (2004) vol. 6 (5) pp. 590-597
doi: 10.1055/s-2004-821090
http://www.thieme-connect.com/DOI/DOI?10.1055/s-2004-821090
Bruno Smadja, Xavier Latour, Sameh Trigui, Jean François Burini, Sylvie Chevalier, Nicole Orange.
Erwinia carotovora subsp. atroseptica and Erwinia carotovora subsp. carotovora can cause substantial damage to economically important plant crops and stored products. The occurrence of the disease and the scale of the damage are temperature dependent. Disease development consists first of active multiplication of the bacteria in the infection area and then production of numerous extracellular enzymes. We investigated the effects of various temperatures on these two steps. We assayed the specific growth rate and the pectate lyase and protease activities for eight strains belonging to E. carotovora subsp. atroseptica and E. carotovora subsp. carotovora in vitro. The temperature effect on growth rate and on pectate lyase activity is different for the two subspecies, but protease activity appears to be similarly thermoregulated. Our results are in agreement with ecological data implicating E. carotovora subsp. atroseptica in disease when the temperature is below 20 degrees C. The optimal temperature for pathogenicity appears to be different from the optimal growth temperature but seems to be a compromise between this temperature and temperatures at which lytic activities are maximal. - Canadian journal of microbiology (2004) vol. 50 (1) pp. 19-27
doi: 10.1139/w03-099
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=15052318&dopt=abstractplus
Regulation of the cytotoxic effects of Pseudomonas fluorescens by growth temperature.
Laurent Picot, Sana Mezghani-Abdelmoula, Sylvie Chevalier, Annabelle Merieau, Olivier Lesouhaitier, Josette Guerillon, Lionel Cazin, Nicole Orange, Marc G J Feuilloley.
We had previously shown that the psychrotrophic bacterium Pseudomonas fluorescens can act as a pathogen, inducing apoptosis and necrosis in neurons and glial cells. In the present study, we investigated the influence of the growth temperature of P. fluorescens on its infectious potential. Adherence of P. fluorescens to glial cells was found to be maximal with bacteria grown at a low temperature (8 degrees C). At that temperature the swimming behaviour was markedly reduced. An increase in the growth temperature to 19, 28 or 32 degrees C strongly diminished the binding of bacteria to host cells. Thus, the adhesion phenotype of P. fluorescens appears to be independent of the motility of the bacteria. The apoptotic effect of P. fluorescens, determined by morphological (nuclear condensation) and biochemical (induction of nitric oxide synthase activity) indicators, correlated well with its binding activity on glial cells. In contrast, there was a clear dissociation between maximum binding and maximal necrotic action (measured by the release of lactate dehydrogenase) observed with bacteria grown at 19 degrees C. As suggested by capillary electrophoresis analysis, the differences in apoptotic effects may be related to variations in the molecular structure of LPS originating from bacteria grown at low and high temperatures, whereas the necrotic effect, which was maximal at the optimum temperature for the secretion of exoenzymes, could reflect variations in the metabolic activity of bacteria. - Research in microbiology (2004) vol. 155 (1) pp. 39-46
doi: 10.1016/j.resmic.2003.09.014
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-49VC608-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9934e66528de4664f3be764e5cd7483f
Pore size dependence on growth temperature is a common characteristic of the major outer membrane protein OprF in psychrotrophic and mesophilic Pseudomonas species.
Thomas Jaouen, Emmanuelle Dé, Sylvie Chevalier, Nicole Orange.
Pseudomonas species adapt well to hostile environments, which are often subjected to rapid variations. In these bacteria, the outer membrane plays an important role in the sensing of environmental conditions such as temperature. In previous studies, it has been shown that in the psychrotrophic strain P. fluorescens MF0, the major porin OprF changes its channel size according to the growth conditions and could affect outer membrane permeability. Studies of the channel-forming properties of OprFs from P. putida 01G3 and P. aeruginosa PAO1 in planar lipid bilayers generated similar results. The presence of a cysteine- or proline-rich cluster in the central linker region is not essential for channel size modulations. These findings suggest that OprF could adopt two alternative conformations in the outer membrane and that folding is thermoregulated. In contrast, no difference according to growth temperature was observed for structurally different outer membrane proteins, such as OprE3 from the Pseudomonas OprD family of specific porins. Our results are consistent with the fact that the decrease in channel size observed at low growth temperature is a particular feature of the OprF porin in various psychrotrophic and mesophilic Pseudomonas species isolated from diverse ecological niches. The ability to reduce outer membrane permeability at low growth temperature could provide these bacteria with adaptive advantages. - Applied and environmental microbiology (2004) vol. 70 (11) pp. 6665-9
doi: 10.1128/AEM.70.11.6665-6669.2004
http://aem.asm.org/cgi/content/full/70/11/6665?view=long&pmid=15528532
Phylogenetic relationships between environmental and clinical isolates of Pseudomonas fluorescens and related species deduced from 16S rRNA gene and OprF protein sequences.
Josselin Bodilis, Raphaël Calbrix, Josette Guérillon, Annabelle Mérieau, Barbara Pawlak, Nicole Orange, Sylvie Barray.
The major surface protein of the genus Pseudomonas, OprF, is a non-specific porin that plays an important role in maintenance of cell shape, in growth in a low osmolarity environment, and in adhesion to various supports. The objectives of our study were (i) to carry out a comparative analysis of phylogenies obtained from the OprF protein and from the 16S rRNA gene in 41 isolates from various sources (water, soil, milk and the hospital) and (ii) to investigate the physiological characteristics correlated with the phylogeny of OprF. We report here an important incongruence between the phylogenies of the 16S rRNA gene and the OprF protein. Phylogenetic analysis of 16S rRNA genes grouped Pseudomonas fluorescens isolates into one cluster (termed fluorescens r-cluster) whilst the phylogeny of the OprF protein divided Pseudomonas fluorescens isolates into two quite distinct clusters (termed fluorescens 1 o-cluster and fluorescens 2 o-cluster) that may be related to the original habitat of the strain. The fluorescens 1 o-cluster contained the majority of non-rhizospheric soil isolates, while the fluorescens 2 o-cluster contained all our clinical isolates and most of the rhizospheric isolates (which are fixed to the roots). In order to check this correlation, we studied two physiological characteristics: the range of growth temperature and the capacity for non-specific adhesion to polystyrene. The temperature range study for strains did not explain the existence of the two o-clusters but it did confirm the capacity of certain P. fluorescens strains to grow at 37 degrees C. The adhesion capacities of the isolates in the two o-clusters seems to be correlated with ecological niche. - Systematic and applied microbiology (2004) vol. 27 (1) pp. 93-108
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=15053326&dopt=abstractplus
Modelling and simulating biological processes in the genomic era: an account of a multidisciplinary thematic school held in Evry (France) in April 2004.
F Képès, P Amar, G Barlovatz, G Bernot, C Froidevaux, JL Giavitto, J Guespin, F Molina, V Norris, V Schächter, P Tracqui.
J. Biol. Phys. Chem. (2004) vol. 4 pp. 131–136
Les réseaux de régulation biologique : rencontre entre biologie et informatique : Production de mucus chez P. aeruginosa = The network of biological regulation: encounter between biology and computer science: mucus production in P. aeruginosa.
J Guespin, G Bernot, J Comet.
TSI. Technique et science informatiques (2004) vol. 23 (7) pp. 939-945
http://cat.inist.fr/?aModele=afficheN&cpsidt=16512123
Involvement of N-acylhomoserine lactones throughout plant infection by Erwinia carotovora subsp. atroseptica (Pectobacterium atrosepticum).
Bruno Smadja, Xavier Latour, Denis Faure, Sylvie Chevalier, Yves Dessaux, Nicole Orange.
Erwinia carotovora subsp. atroseptica is responsible for potato blackleg disease in the field and tuber soft rot during crop storage. The process leading to the disease occurs in two phases: a primary invasion step followed by a maceration step. Bacteria-to-bacteria communication is associated with a quorum-sensing (QS) process based on the production of N-acylhomoserine lactones (HSL). The role of HSL throughout plant infection was analyzed. To this purpose, HSL produced by a specific E. carotovora subsp. atroseptica wild-type strain, which was particularly virulent on potato, were identified. A derivative of this strain that expressed an HSL lactonase gene and produced low amounts of HSL was generated. The comparison of these strains allowed the evaluation of the role of HSL and QS in disease establishment and development. Bacterial growth and motility; activity of proteins secreted by type I, II, and III systems; and hypersensitive and maceration reactions were evaluated. Results indicated that HSL production and QS regulate only those traits involved in the second stage of the host plant infection (i.e., tissue maceration) and hypersensitive response in nonhost tobacco plants. Therefore, the use of QS quenching strategies for biological control in E. carotovora subsp. atroseptica cannot prevent initial infection and multiplication of this pathogen. - Molecular plant-microbe interactions : MPMI (2004) vol. 17 (11) pp. 1269-78
doi: 10.1094/MPMI.2004.17.11.1269
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=15553252&dopt=abstractplus
Epigenesis and dynamic similarity in two regulatory networks in Pseudomonas aeruginosa.
Janine F Guespin-Michel, Gilles Bernot, Jean Paul Comet, Annabelle Mérieau, Adrien Richard, Christian Hulen, Benoit Polack.
Mucoidy and cytotoxicity arise from two independent modifications of the phenotype of the bacterium Pseudomonas aeruginosa that contribute to the mortality and morbidity of cystic fibrosis. We show that, even though the transcriptional regulatory networks controlling both processes are quite different from a molecular or mechanistic point of view, they may be identical from a dynamic point of view: epigenesis may in both cases be the cause of the acquisition of these new phenotypes. This was highlighted by the identity of formal graphs modelling these networks. A mathematical framework based on formal methods from computer science was defined and implemented with a software environment. It allows an easy and rigorous validation and certification of these models and of the experimental methods that can be proposed to falsify or validate the underlying hypothesis. - Acta biotheoretica (2004) vol. 52 (4) pp. 379-90
doi:10.1023/B:ACBI.0000046604.18092.a7
http://www.springerlink.com/content/l701x187324r51uu/
Application of formal methods to biological regulatory networks: extending Thomas' asynchronous logical approach with temporal logic.
Gilles Bernot, Jean-Paul Comet, Adrien Richard, Janine Guespin.
Based on the discrete definition of biological regulatory networks developed by René Thomas, we provide a computer science formal approach to treat temporal properties of biological regulatory networks, expressed in computational tree logic. It is then possible to build all the models satisfying a set of given temporal properties. Our approach is illustrated with the mucus production in Pseudomonas aeruginosa. This application of formal methods from computer science to biological regulatory networks should open the way to many other fruitful applications. - Journal of theoretical biology (2004) vol. 229 (3) pp. 339-47
doi: 10.1016/j.jtbi.2004.04.003
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WMD-4CGM88S-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ba6b5152987921c37e5ff30be9408c7f
A logical (discrete) formulation for the storage and recall of environmental signals in plants.
M Thellier, J Demongeot, V Norris, J Guespin, C Ripoll, R Thomas.
When subjected to an appropriate asymmetric stimulus, seedlings of Bidens pilosa L. "store" a symmetry-breaking instruction that will finally take effect (in the form of a differential growth of the cotyledonary buds) only if the plants are in a state in which they can "recall" this information. The ability of the plants to recall the stored symmetry-breaking instruction may be switched "on" or "off" by the application of a variety of stimuli. Although its detailed phenomenology is rather complicated, the overall behaviour of the plant storage/recall system can be modelled by use of an asynchronous, logical (discrete) description involving positive and negative feedback circuits, which are required for the existence of multi-stationarity and stability, respectively. The state tables, as used in this formalism, give a concise and easy-to-handle description of the evolution of the system and make it particularly easy to determine its stable states. This modelling approach may be extended to the formulation of many other experimental systems. - Plant biology (Stuttgart, Germany) (2004) vol. 6 (5) pp. 590-597
doi: 10.1055/s-2004-821090
http://www.thieme-connect.com/DOI/DOI?10.1055/s-2004-821090
Pseudomonas fluorescens lipopolysaccharide inhibits both delayed rectifier and transient A-type K+ channels of cultured rat cerebellar granule neurons.
Sana Mezghani-Abdelmoula, Sylvie Chevalier, Olivier Lesouhaitier, Nicole Orange, Marc G J Feuilloley, Lionel Cazin.
Pseudomonas fluorescens is a Gram-negative bacillus closely related to the pathogen P. aeruginosa known to provoke infectious disorders in the central nervous system (CNS). The endotoxin lipopolysaccharide (LPS) expressed by the bacteria is the first infectious factor that can interact with the plasma membrane of host cells. In the present study, LPS extracted from P. fluorescens MF37 was examined for its actions on delayed rectifier and A-type K(+) channels, two of the main types of voltage-activated K(+) channels involved in the action potential firing. Current recordings were performed in cultured rat cerebellar granule neurons at days 7 or 8, using the whole-cell patch-clamp technique. A 3-h incubation with LPS (200 ng/ml) markedly depressed both the delayed rectifier (I(KV)) and transient A-type (I(A)) K(+) currents evoked by depolarizations above 0 and -40 mV, respectively. The percent decrease of I(KV) and I(A) ( approximately 30%) did not vary with membrane potential, suggesting that inhibition of both types of K(+) channels by LPS was voltage-insensitive. The endotoxin did neither modify the steady-state voltage-dependent activation properties of I(KV) and I(A) nor the steady-state inactivation of I(A). The present results suggest that, by inhibiting I(KV) and I(A), LPS applied extracellulary increases the action potential firing in cerebellar granule neurons. It is concluded that P. fluorescens MF37 may provoke in the CNS disorders associated with sever alterations of membrane ionic channel functions. - Brain research (2003) vol. 983 (1-2) pp. 185-92
doi: 10.1016/S0006-8993(03)03055-5
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6SYR-48Y0D9S-G&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=493698778253048ad70a28a0bf431ce9
Modelling, observability and experiment: a case study.- Positive feedback loop in a genetic regulatory network
G Bernot, J Guespin-Michel, J Comet, P Amar, F Delaplace, P Ballet.
We propose an interdisciplinary methodology for biological modelling inspired by the design and validation of large computing systems. To know if a model for biology can be satisfactorily validated by a set of experiments seems to be a natural and necessary constraint for its definition. Defining a model should go with experimental methods and conditions able to validate or invalidate it. As in the design of large sized softwares, we will distinguish two activities : first to build an accurate model specifying the observed behaviour, second to design plans of experiments to verify a posteriori the model predictions.
We wish to experiment, through the case of the modelling of the mucus production by the bacterium Pseudomonas aeruginosa, the application of this working methodology. - Proceedings of the Dieppe spring school, edited by Amar et al. (2003) pp. 49-56
http://www.i3s.unice.fr/~comet/publications/RapportsRecherche/RR2002-1.pdf
Modelling and simulation of biological processes in the context of genomics.
V Norris, P Amar, G Bernot, J Giavitto, C Godin, Janine Guespin, H Pollard, Philippe Tracqui, Francois Kepes.
Journal of Biological Physics and Chemistry (2003) vol. 3 pp. 106-110
http://www.i3s.unice.fr/~bernot/Biomodels/2003-JBPC-School.pdf
Involvement of Pseudomonas and related species in central nervous system infections.
M Feuilloley, S-Mezghani-Abdelmoula, Laurent Picot, O Lesouhaitier, A Mérieau, J Guérillon, N Boujedaïni, Lionel Cazin, N Orange.
Even in developed countries where antibiotic therapy is easily and rapidly accessible, central nervous system (CNS) infections remain an important cause of morbidity and mortality. Besides the well known opportunistic pathogen P. aeruginosa, which can be responsible for several forms of CNS infections including meningitis, ventriculitis or brain abscesses, there is now ample evidence that the infectious potential of several non-P. aeruginosa species such as P. putida, P. fluorescens or P. stutzeri should be taken into consideration. The physiological properties and evolutionary potential of these species show that they represent and increasing threat, especially in the framework of CNS infections. Former Pseudomonas, nowadays identified under other taxon such as Burkholderia, Chryseomonas or Stenotrophomonas, and species closely related are also presenting a noticeable infectious potential in regard of the CNS. Some of these bacteria are now well recognized as emerging pathogens but this review reveals that the role of Pseudomonas and related species is frequently underestimated for several reasons: (I) the difficulty of identification of the causative agent of the disease, (II) the insidious and sometimes extremely slow development of the infection, (III) the possible indirect effect of the bacteria and (IV) the habit to consider Pseudomonas essentially as opportunistic bacteria in respiratory tract infections. The role of Pseudomonas and related species in CNS infections is discussed in detail using more recent findings of the bacterial taxonomy. - Recent Research Developments in Microbiology (2003) vol. 7 pp. 55-71
http://www.cababstractsplus.org/abstracts%5C/Abstract.aspx?AcNo=20043044431
Cytotoxic effects of the lipopolysaccharide from Pseudomonas fluorescens on neurons and glial cells.
Laurent Picot, Sylvie Chevalier, Sana Mezghani-Abdelmoula, Annabelle Merieau, Olivier Lesouhaitier, Philippe Leroux, Lionel Cazin, Nicole Orange, Marc G J Feuilloley.
Pseudomonas fluorescens is an emerging pathogen closely related to Pseudomonas aeruginosa. In the present study, the effect of the lipopolysaccharide (LPS) from P. fluorescens MF37 was investigated using indicators of apoptosis and necrosis and was compared to the effect of the LPS from P. aeruginosa PAO1. Capillary electrophoresis analysis of the LPS from P. fluorescens MF37 revealed the existence of three forms of the endotoxin and the absence of homology with the LPS from P. aeruginosa. In neurons and glial cells the LPS from P. fluorescens induced major morphological changes including a condensation of the cytoplasmic proteins, a leakage of the cytoplasmic content, the formation of blebs on the nuclear membrane and a marked reorganization of the cytoskeleton. In glial cells, the LPS from P. fluorescens provoked the migration of phosphatidylserine at the surface of the cytoplasmic membrane, a sign of apoptosis, but this reaction was associated to an increase in the permeability to propidium iodide characteristic of necrosis. Biochemical studies revealed an important activation of an inducible nitric oxide synthase and a release of lactate dehydrogenase, a stable cytosolic enzyme. These results demonstrate that the LPS from P. fluorescens induces apoptosis and a concomitant and limited necrosis, reveal the unexpected cytotoxicity of this endotoxin and provide the first demonstration of the apoptotic effect of a non-aeruginosa Pseudomonas on nerve cells. - Microbial pathogenesis (2003) vol. 35 (3) pp. 95-106
doi: 10.1016/S0882-4010(03)00092-5
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WN6-494C7FS-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=b9b2ff7a112c697caa642dd350750360
Bacterial adaptation and epigenesis. Recent research and Developments .
J Guespin-Michel, B Polack, A Merieau.
Heritable but non-genetic modifications, i.e. epigenetic modifications, are not restricted to eukaryotes. These modifications, which are often reversible, have also been observed in prokaryotes. We analyse here two such cases where positive feedback circuits are essential for the occurrence of epigenesis. The properties of epigenetic modifications that can be drawn from these examples are in good agreement with the fact that epigenesis in bacteria is the biological equivalent of multistationarity in physics, for which mathematical models are readily available.
Epigenetic modifications (or multistationarity) are likely to occur in many situations where bacteria adapt to changes in their environment. To validate this hypothesis, model-driven experiments are necessary. This opens up a whole new field that may provide new opportunities for applied or therapeutic usages. - Microbiology (2003) vol. 7 pp. 289-305
Sana Mezghani-Abdelmoula, Sylvie Chevalier, Olivier Lesouhaitier, Nicole Orange, Marc G J Feuilloley, Lionel Cazin.
Pseudomonas fluorescens is a Gram-negative bacillus closely related to the pathogen P. aeruginosa known to provoke infectious disorders in the central nervous system (CNS). The endotoxin lipopolysaccharide (LPS) expressed by the bacteria is the first infectious factor that can interact with the plasma membrane of host cells. In the present study, LPS extracted from P. fluorescens MF37 was examined for its actions on delayed rectifier and A-type K(+) channels, two of the main types of voltage-activated K(+) channels involved in the action potential firing. Current recordings were performed in cultured rat cerebellar granule neurons at days 7 or 8, using the whole-cell patch-clamp technique. A 3-h incubation with LPS (200 ng/ml) markedly depressed both the delayed rectifier (I(KV)) and transient A-type (I(A)) K(+) currents evoked by depolarizations above 0 and -40 mV, respectively. The percent decrease of I(KV) and I(A) ( approximately 30%) did not vary with membrane potential, suggesting that inhibition of both types of K(+) channels by LPS was voltage-insensitive. The endotoxin did neither modify the steady-state voltage-dependent activation properties of I(KV) and I(A) nor the steady-state inactivation of I(A). The present results suggest that, by inhibiting I(KV) and I(A), LPS applied extracellulary increases the action potential firing in cerebellar granule neurons. It is concluded that P. fluorescens MF37 may provoke in the CNS disorders associated with sever alterations of membrane ionic channel functions. - Brain research (2003) vol. 983 (1-2) pp. 185-92
doi: 10.1016/S0006-8993(03)03055-5
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6SYR-48Y0D9S-G&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=493698778253048ad70a28a0bf431ce9
Modelling, observability and experiment: a case study.- Positive feedback loop in a genetic regulatory network
G Bernot, J Guespin-Michel, J Comet, P Amar, F Delaplace, P Ballet.
We propose an interdisciplinary methodology for biological modelling inspired by the design and validation of large computing systems. To know if a model for biology can be satisfactorily validated by a set of experiments seems to be a natural and necessary constraint for its definition. Defining a model should go with experimental methods and conditions able to validate or invalidate it. As in the design of large sized softwares, we will distinguish two activities : first to build an accurate model specifying the observed behaviour, second to design plans of experiments to verify a posteriori the model predictions.
We wish to experiment, through the case of the modelling of the mucus production by the bacterium Pseudomonas aeruginosa, the application of this working methodology. - Proceedings of the Dieppe spring school, edited by Amar et al. (2003) pp. 49-56
http://www.i3s.unice.fr/~comet/publications/RapportsRecherche/RR2002-1.pdf
Modelling and simulation of biological processes in the context of genomics.
V Norris, P Amar, G Bernot, J Giavitto, C Godin, Janine Guespin, H Pollard, Philippe Tracqui, Francois Kepes.
Journal of Biological Physics and Chemistry (2003) vol. 3 pp. 106-110
http://www.i3s.unice.fr/~bernot/Biomodels/2003-JBPC-School.pdf
Involvement of Pseudomonas and related species in central nervous system infections.
M Feuilloley, S-Mezghani-Abdelmoula, Laurent Picot, O Lesouhaitier, A Mérieau, J Guérillon, N Boujedaïni, Lionel Cazin, N Orange.
Even in developed countries where antibiotic therapy is easily and rapidly accessible, central nervous system (CNS) infections remain an important cause of morbidity and mortality. Besides the well known opportunistic pathogen P. aeruginosa, which can be responsible for several forms of CNS infections including meningitis, ventriculitis or brain abscesses, there is now ample evidence that the infectious potential of several non-P. aeruginosa species such as P. putida, P. fluorescens or P. stutzeri should be taken into consideration. The physiological properties and evolutionary potential of these species show that they represent and increasing threat, especially in the framework of CNS infections. Former Pseudomonas, nowadays identified under other taxon such as Burkholderia, Chryseomonas or Stenotrophomonas, and species closely related are also presenting a noticeable infectious potential in regard of the CNS. Some of these bacteria are now well recognized as emerging pathogens but this review reveals that the role of Pseudomonas and related species is frequently underestimated for several reasons: (I) the difficulty of identification of the causative agent of the disease, (II) the insidious and sometimes extremely slow development of the infection, (III) the possible indirect effect of the bacteria and (IV) the habit to consider Pseudomonas essentially as opportunistic bacteria in respiratory tract infections. The role of Pseudomonas and related species in CNS infections is discussed in detail using more recent findings of the bacterial taxonomy. - Recent Research Developments in Microbiology (2003) vol. 7 pp. 55-71
http://www.cababstractsplus.org/abstracts%5C/Abstract.aspx?AcNo=20043044431
Cytotoxic effects of the lipopolysaccharide from Pseudomonas fluorescens on neurons and glial cells.
Laurent Picot, Sylvie Chevalier, Sana Mezghani-Abdelmoula, Annabelle Merieau, Olivier Lesouhaitier, Philippe Leroux, Lionel Cazin, Nicole Orange, Marc G J Feuilloley.
Pseudomonas fluorescens is an emerging pathogen closely related to Pseudomonas aeruginosa. In the present study, the effect of the lipopolysaccharide (LPS) from P. fluorescens MF37 was investigated using indicators of apoptosis and necrosis and was compared to the effect of the LPS from P. aeruginosa PAO1. Capillary electrophoresis analysis of the LPS from P. fluorescens MF37 revealed the existence of three forms of the endotoxin and the absence of homology with the LPS from P. aeruginosa. In neurons and glial cells the LPS from P. fluorescens induced major morphological changes including a condensation of the cytoplasmic proteins, a leakage of the cytoplasmic content, the formation of blebs on the nuclear membrane and a marked reorganization of the cytoskeleton. In glial cells, the LPS from P. fluorescens provoked the migration of phosphatidylserine at the surface of the cytoplasmic membrane, a sign of apoptosis, but this reaction was associated to an increase in the permeability to propidium iodide characteristic of necrosis. Biochemical studies revealed an important activation of an inducible nitric oxide synthase and a release of lactate dehydrogenase, a stable cytosolic enzyme. These results demonstrate that the LPS from P. fluorescens induces apoptosis and a concomitant and limited necrosis, reveal the unexpected cytotoxicity of this endotoxin and provide the first demonstration of the apoptotic effect of a non-aeruginosa Pseudomonas on nerve cells. - Microbial pathogenesis (2003) vol. 35 (3) pp. 95-106
doi: 10.1016/S0882-4010(03)00092-5
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WN6-494C7FS-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=b9b2ff7a112c697caa642dd350750360
Bacterial adaptation and epigenesis. Recent research and Developments .
J Guespin-Michel, B Polack, A Merieau.
Heritable but non-genetic modifications, i.e. epigenetic modifications, are not restricted to eukaryotes. These modifications, which are often reversible, have also been observed in prokaryotes. We analyse here two such cases where positive feedback circuits are essential for the occurrence of epigenesis. The properties of epigenetic modifications that can be drawn from these examples are in good agreement with the fact that epigenesis in bacteria is the biological equivalent of multistationarity in physics, for which mathematical models are readily available.
Epigenetic modifications (or multistationarity) are likely to occur in many situations where bacteria adapt to changes in their environment. To validate this hypothesis, model-driven experiments are necessary. This opens up a whole new field that may provide new opportunities for applied or therapeutic usages. - Microbiology (2003) vol. 7 pp. 289-305
The Antarctic Psychrobacter sp. TAD1 has two cold-active glutamate dehydrogenases with different cofactor specificities. Characterisation of the NAD+-dependent enzyme.
Laura Camardella, Raffaela Di Fraia, Antonella Antignani, M Antonietta Ciardiello, Guido di Prisco, Julie K Coleman, Laurent Buchon, Janine Guespin, Nicholas J Russell.
Psychrobacter sp. TAD1 is a psychrotolerant bacterium from Antarctic frozen continental water that grows from 2 to 25 degrees C with optimal growth rate at 20 degrees C. The new isolate contains two glutamate dehydrogenases (GDH), differing in their cofactor specificities, subunit sizes and arrangements, and thermal properties. NADP+-dependent GDH is a hexamer of 47 kDa subunits and it is comparable to other hexameric GDHs of family-I from bacteria and lower eukaria. The NAD+-dependent enzyme, described in this communication, has a subunit weight of 160 kDa and belongs to the novel class of GDHs with large size subunits. The enzyme is a dimer; this oligomeric arrangement has not been reported previously for GDH. Both enzymes have an apparent optimum temperature for activity of approximately 20 degrees C, but their cold activities and thermal labilities are different. The NAD+-dependent enzyme is more cold active: at 10 C it retains 50% of its maximal activity, compared with 10% for the NADP+-dependent enzyme. The NADP+-dependent enzyme is more heat stable, losing only 10% activity after heating for 30 min, compared with 95% for the NAD+-dependent enzyme. It is concluded that in Psychrobacter sp. TAD1 not only does NAD+-dependent GDH have a novel subunit molecular weight and arrangement, but that its polypeptide chains are folded differently from those of NADP+-dependent GDH, providing different cold-active properties to the two enzymes. - Comparative biochemistry and physiology Part A, Molecular & integrative physiology (2002) vol. 131 (3) pp. 559-67
doi: 10.1016/S1095-6433(01)00507-4
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VNH-44YF922-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=e0ec3c4982159eef966bdb6a02475787
Porins of Pseudomonas fluorescens MFO as fibronectin-binding proteins.
Rebière-Huët, J Guérillon, A Pimenta, P Di Martin, N Orange, C Hulen.
Bacterial adherence is a complex phenomenon involving specific interactions between receptors, including matricial fibronectin, and bacterial ligands. We show here that fibronectin and outer membrane proteins of Pseudomonas fluorescens were able to inhibit adherence of P. fluorescens to fibronectin-coated wells. We identified at least six fibronectin-binding proteins with molecular masses of 70, 55, 44, 37, 32 and 28 kDa. The presence of native (32 kDa) and heat-modified forms (37 kDa) of OprF was revealed by immuno-analysis and the 44-kDa band was composed of three proteins, their N-terminal sequences showing homologies with Pseudomonas aeruginosa porins (OprD, OprE1 and OprE3). - FEMS microbiology letters (2002) vol. 215 (1) pp. 121 - 126
doi: 10.1111/j.1574-6968.2002.tb11380.x
http://www3.interscience.wiley.com/journal/118919084/abstract
Multistationarity and positive feedback circuits
J Guespin-Michel.
Modelling and simulation of biological process in the context of genomics. (proceedings of the Autrans seminar march 18th-21st/03/2002). edited by Kepes et al. (2002) pp. 193-202
Modeling and Simulating Biological Processes in the Genomic Aera: an account of a multidisciplinary seminar held in Autrans (France) in March, 2002.
F Képès, F Delaplace, J Delosme, JF Guespin, Roberto Incitti, Vic Norris.
.J. Biol. Phys. Chem. (2002) vol. 2 pp. 62-66
http://www.iubs.org/newiubs/products/bioint/BioInt%20PDF1/BI%20Regular%20Issues/BI%20Numero%2043.pdf
Isolation of an Escherichia coli strain mutant unable to form biofilm on polystyrene and to adhere to human pneumocyte cells: involvement of tryptophanase.
P Di Martino, A Merieau, R Phillips, N Orange, C Hulen.
Escherichia coli adherence to biotic and abiotic surfaces constitutes the first step of infection by promoting colonization and biofilm formation. The aim of this study was to gain a better understanding of the relationship between E. coli adherence to different biotic surfaces and biofilm formation on abiotic surfaces. We isolated mutants defective in A549 pneumocyte cells adherence, fibronectin adherence, and biofilm formation by random transposition mutagenesis and sequential passages over A549 cell monolayers. Among the 97 mutants tested, 80 were decreased in biofilm formation, 8 were decreased in A549 cells adherence, 7 were decreased in their adherence to fibronectin, and 17 had no perturbations in either of the three phenotypes. We observed a correlation between adherence to fibronectin or A549 cells and biofilm formation, indicating that biotic adhesive factors are involved in biofilm formation by E. coli. Molecular analysis of the mutants revealed that a transposon insertion in the tnaA gene encoding for tryptophanase was associated with a decrease in both A549 cells adherence and biofilm formation by E. coli. The complementation of the tnaA mutant with plasmid-located wild-type tnaA restored the tryptophanase activity, epithelial cells adherence, and biofilm formation on polystyrene. The possible mechanism of tryptophanase involvement in E. coli adherence and biofilm formation is discussed. - Canadian journal of microbiology (2002) vol. 48 (2) pp. 132-137
doi: 10.1139/w02-001
http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1480-3275&volume=48&issue=2&startPage=132&ab=y
Hyperstructures, genome analysis and I-cells.
Patrick Amar, Pascal Ballet, Georgia Barlovatz-Meimon, Arndt Benecke, Gilles Bernot, Yves Bouligand, Paul Bourguine, Franck Delaplace, Jean-Marc Delosme, Maurice Demarty, Itzhak Fishov, Jean Fourmentin-Guilbert, Joe Fralick, Jean-Louis Giavitto, Bernard Gleyse, Christophe Godin, Roberto Incitti, François Képès, Catherine Lange, Lois Le Sceller, Corinne Loutellier, Olivier Michel, Franck Molina, Chantal Monnier, René Natowicz, Vic Norris, Nicole Orange, Helene Pollard, Derek Raine, Camille Ripoll, Josette Rouviere-Yaniv, Milton Saier, Paul Soler, Pierre Tambourin, Michel Thellier, Philippe Tracqui, Dave Ussery, Jean-Claude Vincent, Jean-Pierre Vannier, Philippa Wiggins, Abdallah Zemirline.
New concepts may prove necessary to profit from the avalanche of sequence data on the genome, transcriptome, proteome and interactome and to relate this information to cell physiology. Here, we focus on the concept of large activity-based structures, or hyperstructures, in which a variety of types of molecules are brought together to perform a function. We review the evidence for the existence of hyperstructures responsible for the initiation of DNA replication, the sequestration of newly replicated origins of replication, cell division and for metabolism. The processes responsible for hyperstructure formation include changes in enzyme affinities due to metabolite-induction, lipid-protein affinities, elevated local concentrations of proteins and their binding sites on DNA and RNA, and transertion. Experimental techniques exist that can be used to study hyperstructures and we review some of the ones less familiar to biologists. Finally, we speculate on how a variety of in silico approaches involving cellular automata and multi-agent systems could be combined to develop new concepts in the form of an Integrated cell (I-cell) which would undergo selection for growth and survival in a world of artificial microbiology. - Acta biotheoretica (2002) vol. 50 (4) pp. 357-73
http://www.springerlink.com/content/t715633765n48p12/
Laura Camardella, Raffaela Di Fraia, Antonella Antignani, M Antonietta Ciardiello, Guido di Prisco, Julie K Coleman, Laurent Buchon, Janine Guespin, Nicholas J Russell.
Psychrobacter sp. TAD1 is a psychrotolerant bacterium from Antarctic frozen continental water that grows from 2 to 25 degrees C with optimal growth rate at 20 degrees C. The new isolate contains two glutamate dehydrogenases (GDH), differing in their cofactor specificities, subunit sizes and arrangements, and thermal properties. NADP+-dependent GDH is a hexamer of 47 kDa subunits and it is comparable to other hexameric GDHs of family-I from bacteria and lower eukaria. The NAD+-dependent enzyme, described in this communication, has a subunit weight of 160 kDa and belongs to the novel class of GDHs with large size subunits. The enzyme is a dimer; this oligomeric arrangement has not been reported previously for GDH. Both enzymes have an apparent optimum temperature for activity of approximately 20 degrees C, but their cold activities and thermal labilities are different. The NAD+-dependent enzyme is more cold active: at 10 C it retains 50% of its maximal activity, compared with 10% for the NADP+-dependent enzyme. The NADP+-dependent enzyme is more heat stable, losing only 10% activity after heating for 30 min, compared with 95% for the NAD+-dependent enzyme. It is concluded that in Psychrobacter sp. TAD1 not only does NAD+-dependent GDH have a novel subunit molecular weight and arrangement, but that its polypeptide chains are folded differently from those of NADP+-dependent GDH, providing different cold-active properties to the two enzymes. - Comparative biochemistry and physiology Part A, Molecular & integrative physiology (2002) vol. 131 (3) pp. 559-67
doi: 10.1016/S1095-6433(01)00507-4
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VNH-44YF922-1&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=e0ec3c4982159eef966bdb6a02475787
Porins of Pseudomonas fluorescens MFO as fibronectin-binding proteins.
Rebière-Huët, J Guérillon, A Pimenta, P Di Martin, N Orange, C Hulen.
Bacterial adherence is a complex phenomenon involving specific interactions between receptors, including matricial fibronectin, and bacterial ligands. We show here that fibronectin and outer membrane proteins of Pseudomonas fluorescens were able to inhibit adherence of P. fluorescens to fibronectin-coated wells. We identified at least six fibronectin-binding proteins with molecular masses of 70, 55, 44, 37, 32 and 28 kDa. The presence of native (32 kDa) and heat-modified forms (37 kDa) of OprF was revealed by immuno-analysis and the 44-kDa band was composed of three proteins, their N-terminal sequences showing homologies with Pseudomonas aeruginosa porins (OprD, OprE1 and OprE3). - FEMS microbiology letters (2002) vol. 215 (1) pp. 121 - 126
doi: 10.1111/j.1574-6968.2002.tb11380.x
http://www3.interscience.wiley.com/journal/118919084/abstract
Multistationarity and positive feedback circuits
J Guespin-Michel.
Modelling and simulation of biological process in the context of genomics. (proceedings of the Autrans seminar march 18th-21st/03/2002). edited by Kepes et al. (2002) pp. 193-202
Modeling and Simulating Biological Processes in the Genomic Aera: an account of a multidisciplinary seminar held in Autrans (France) in March, 2002.
F Képès, F Delaplace, J Delosme, JF Guespin, Roberto Incitti, Vic Norris.
.J. Biol. Phys. Chem. (2002) vol. 2 pp. 62-66
http://www.iubs.org/newiubs/products/bioint/BioInt%20PDF1/BI%20Regular%20Issues/BI%20Numero%2043.pdf
Isolation of an Escherichia coli strain mutant unable to form biofilm on polystyrene and to adhere to human pneumocyte cells: involvement of tryptophanase.
P Di Martino, A Merieau, R Phillips, N Orange, C Hulen.
Escherichia coli adherence to biotic and abiotic surfaces constitutes the first step of infection by promoting colonization and biofilm formation. The aim of this study was to gain a better understanding of the relationship between E. coli adherence to different biotic surfaces and biofilm formation on abiotic surfaces. We isolated mutants defective in A549 pneumocyte cells adherence, fibronectin adherence, and biofilm formation by random transposition mutagenesis and sequential passages over A549 cell monolayers. Among the 97 mutants tested, 80 were decreased in biofilm formation, 8 were decreased in A549 cells adherence, 7 were decreased in their adherence to fibronectin, and 17 had no perturbations in either of the three phenotypes. We observed a correlation between adherence to fibronectin or A549 cells and biofilm formation, indicating that biotic adhesive factors are involved in biofilm formation by E. coli. Molecular analysis of the mutants revealed that a transposon insertion in the tnaA gene encoding for tryptophanase was associated with a decrease in both A549 cells adherence and biofilm formation by E. coli. The complementation of the tnaA mutant with plasmid-located wild-type tnaA restored the tryptophanase activity, epithelial cells adherence, and biofilm formation on polystyrene. The possible mechanism of tryptophanase involvement in E. coli adherence and biofilm formation is discussed. - Canadian journal of microbiology (2002) vol. 48 (2) pp. 132-137
doi: 10.1139/w02-001
http://article.pubs.nrc-cnrc.gc.ca/ppv/RPViewDoc?issn=1480-3275&volume=48&issue=2&startPage=132&ab=y
Hyperstructures, genome analysis and I-cells.
Patrick Amar, Pascal Ballet, Georgia Barlovatz-Meimon, Arndt Benecke, Gilles Bernot, Yves Bouligand, Paul Bourguine, Franck Delaplace, Jean-Marc Delosme, Maurice Demarty, Itzhak Fishov, Jean Fourmentin-Guilbert, Joe Fralick, Jean-Louis Giavitto, Bernard Gleyse, Christophe Godin, Roberto Incitti, François Képès, Catherine Lange, Lois Le Sceller, Corinne Loutellier, Olivier Michel, Franck Molina, Chantal Monnier, René Natowicz, Vic Norris, Nicole Orange, Helene Pollard, Derek Raine, Camille Ripoll, Josette Rouviere-Yaniv, Milton Saier, Paul Soler, Pierre Tambourin, Michel Thellier, Philippe Tracqui, Dave Ussery, Jean-Claude Vincent, Jean-Pierre Vannier, Philippa Wiggins, Abdallah Zemirline.
New concepts may prove necessary to profit from the avalanche of sequence data on the genome, transcriptome, proteome and interactome and to relate this information to cell physiology. Here, we focus on the concept of large activity-based structures, or hyperstructures, in which a variety of types of molecules are brought together to perform a function. We review the evidence for the existence of hyperstructures responsible for the initiation of DNA replication, the sequestration of newly replicated origins of replication, cell division and for metabolism. The processes responsible for hyperstructure formation include changes in enzyme affinities due to metabolite-induction, lipid-protein affinities, elevated local concentrations of proteins and their binding sites on DNA and RNA, and transertion. Experimental techniques exist that can be used to study hyperstructures and we review some of the ones less familiar to biologists. Finally, we speculate on how a variety of in silico approaches involving cellular automata and multi-agent systems could be combined to develop new concepts in the form of an Integrated cell (I-cell) which would undergo selection for growth and survival in a world of artificial microbiology. - Acta biotheoretica (2002) vol. 50 (4) pp. 357-73
http://www.springerlink.com/content/t715633765n48p12/
Pseudomonas fluorescens as a potential pathogen: adherence to nerve cells.
L Picot, S M Abdelmoula, A Merieau, P Leroux, L Cazin, N Orange, M G Feuilloley.
In order to determine the infectious potential of the psychrotrophic bacterium Pseudomonas fluorescens, a species closely related to the opportunistic pathogen P. aeruginosa, we investigated the binding activity of this bacterium on primary cultures of rat neonate cortical neurons and glial cells, adrenal paraneurons and NG108-15 neuroblastoma cells. Incubated at concentrations of 10(6) and 10(8) CFU/mL, P. fluorescens MF37 exhibited a high binding activity on neurons in the same range as that of P. aeruginosa PAO1. A significant, but lower, adherence of P. fluorescens was also detected on glial cells and adrenal paraneurons. In contrast, when P. fluorescens MF37 or P. aeruginosa PAO1 were incubated with neuroblastoma cells, no binding was observed. In neurons, the association of P. fluorescens with the plasma membrane occurred both on neurites and cell body. Leakage of the cytoplasmic content was frequently noted. Studies performed using the fluorescent probe Hoechst 33258 revealed that in 10% of neurons, P. fluorescens induced the appearance of densely stained clusters of DNA that was typical of an early step of apoptosis. In glial cells exposed to P. fluorescens, marked changes in the morphology of the nucleus, including fragmentation into lobular structures and aggregation of DNA, were also reminiscent of the existence of a possible apoptotic mechanism. Taken together, these results reveal that P. fluorescens can bind to nerve cells and affect their physiology and, in agreement with recent clinical observations, suggest that P. fluorescens could behave as a pathogen. - Microbes and infection / Institut Pasteur (2001) vol. 3 (12) pp. 985-95
doi: 10.1016/S1286-4579(01)01462-9
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VPN-4430Y9K-G&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6d66c158e0410fbe57adb8f570f594e7
Positive feedback circuits and adaptive regulations in bacteria.
J Guespin-Michel, M Kaufman.
The mechanisms by which bacteria adapt to changes in their environment involve transcriptional regulation in which a transcriptional regulator responds to signal(s) from the environment and regulates (positively or negatively) the expression of several genes or operons. Some of these regulators exert a positive feedback on their own expression. This is a necessary (although not sufficient) condition for the occurrence of multistationarity. One biological consequence of multistationarity may be epigenetic modifications, a hypothesis unusual to microbiologists, in spite of some well-known epigenetic modifications in bacteria. We propose here that the occurrence of mucoidy in the opportunistic pathogen Pseudomonas aeruginosa, which is currently attributed to mutations only, may also be an epigenetic modification. A theoretical approach using a generalised logical analysis lends credit to this hypothesis and suggests experiments to ascertain it. - Acta biotheoretica (2001) vol. 49 (4) pp. 207-18
http://www.springerlink.com/content/1crxghpx4hgarqql/
Low pH and cold temperature combine to limit growth and pectate lyase production by the psychrotrophic bacterium Erwinia carotovora ssp. carotovora MFCL0.
P Laurent, L Buchon, J Burini, N Orange.
Growth and pectate lyase production by Erwinia carotovora ssp. carotovora MFCL0 were optimal at 28 °C and 14 °C, respectively. Although cold conditions (8 °C ) have retarded bacterial growth, low temperatures were not sufficient to prevent enzyme production but can be combined with a low pH (5.2) to protect vegetables against this phytopathogen. - Biotechnology Letters (2001)
http://www.springerlink.com/index/T228490U18615572.pdf
Isolation and characterisation of the major outer membrane protein of Erwinia carotovora.
C El Hamel, S Chevalier, E Dé, N Orange, Gérard Molle.
The purified major outer membrane protein (37275 Da) from the psychrotrophic phytopathogen Erwinia carotovora MFCL0 was structurally characterised by MALDI-TOF mass spectrometry, N-terminal microsequencing and DNA sequence determinations, and secondary structure prediction analyses. The deduced amino acid sequence showed 76% and 72% of similarities with the Serratia marcescens and Escherichia coli OmpA proteins respectively. Dendrogram analysis allowed to point out that E. carotovora is close to the genus Serratia. After reconstitution into planar lipid bilayers, this major protein induced ion channels with a major conductance level of 630 pS in 1 M NaCl and a weak cationic selectivity. These functional and structural features allowed to identify this major outer membrane component of E. carotovora as an OmpA-like protein, i.e., a channel-forming protein which could be involved in the infection process of this phytopathogen agent. - BBA-Biomembranes (2001) vol. 1515 (1) pp. 12-22
doi: 10.1016/S0005-2736(01)00387-X
http://linkinghub.elsevier.com/retrieve/pii/S000527360100387X
Estimation of the abundance of the cadmium resistance gene cadA in microbial communities in polluted estuary water.
C Oger, T Berthe, L Quillet, S Barray, J F Chiffoleau, F Petit.
We describe herein a molecular method for estimating the abundance of the cadA gene, which encodes a Cd2+/ATPase protein transporter, in bacterial DNA extracted from samples of environmental water. Competitive polymerase chain reaction (cPCR) may be the most appropriate technique for assessing the prevalence of the cadA gene in microbial communities in highly heterogeneous and polluted environments, such as the Seine estuary (France). We describe the development of this method: (i) the choice of two specific primers, based on the sequences encoding the cadmium binding site and the ion channel domains; (ii) the construction of a competitor sequence and assessment of its amplification efficiency; and (iii) the estimation of the copy number of the cadA gene. The cadA content in the bacterial community is expressed as the number of gene copies per ng of total DNA extracted, which is independent of the DNA extraction yield. This molecular procedure was improved to analyze cadA levels in bacterial DNA extracted from estuary water accidentally contaminated with cadmium. Results revealed a subsequent increase in the copy number of the cadA gene in the microbial community. - Research in microbiology (2001) vol. 152 (7) pp. 671-8
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=11605987&dopt=abstractplus
Epigenesis--a request for information on loss of adaptive phenotypes.
J Guespin-Michel.
Microbiology (Reading, England) (2001) vol. 147 (Pt 2) pp. 252-3
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=11158342&dopt=abstractplus
A novel gene from Myxococcus xanthus that facilitates membrane translocation of an extracellular endoglucanase in Escherichia coli?.
L Bensmail, C Monnier, L Quillet, J F Guespin-Michel, S Barray.
Expression in Escherichia coli of the Myxococcus xanthus gene celA, which encodes an extracellular endoglucanase, resulted in CelA being distributed between cytoplasm, periplasm and membrane. The presence of an adjacent open reading frame downstream from the full celA gene, or the absence of a putative lipoprotein signal sequence, confined CelA distribution to the periplasm and membrane, or to the cytoplasm and periplasm, respectively. - Research in microbiology (2001) vol. 152 (5) pp. 487-92
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-436FB18-9&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9cd693105b7e21de51862265650d2cd2
L Picot, S M Abdelmoula, A Merieau, P Leroux, L Cazin, N Orange, M G Feuilloley.
In order to determine the infectious potential of the psychrotrophic bacterium Pseudomonas fluorescens, a species closely related to the opportunistic pathogen P. aeruginosa, we investigated the binding activity of this bacterium on primary cultures of rat neonate cortical neurons and glial cells, adrenal paraneurons and NG108-15 neuroblastoma cells. Incubated at concentrations of 10(6) and 10(8) CFU/mL, P. fluorescens MF37 exhibited a high binding activity on neurons in the same range as that of P. aeruginosa PAO1. A significant, but lower, adherence of P. fluorescens was also detected on glial cells and adrenal paraneurons. In contrast, when P. fluorescens MF37 or P. aeruginosa PAO1 were incubated with neuroblastoma cells, no binding was observed. In neurons, the association of P. fluorescens with the plasma membrane occurred both on neurites and cell body. Leakage of the cytoplasmic content was frequently noted. Studies performed using the fluorescent probe Hoechst 33258 revealed that in 10% of neurons, P. fluorescens induced the appearance of densely stained clusters of DNA that was typical of an early step of apoptosis. In glial cells exposed to P. fluorescens, marked changes in the morphology of the nucleus, including fragmentation into lobular structures and aggregation of DNA, were also reminiscent of the existence of a possible apoptotic mechanism. Taken together, these results reveal that P. fluorescens can bind to nerve cells and affect their physiology and, in agreement with recent clinical observations, suggest that P. fluorescens could behave as a pathogen. - Microbes and infection / Institut Pasteur (2001) vol. 3 (12) pp. 985-95
doi: 10.1016/S1286-4579(01)01462-9
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VPN-4430Y9K-G&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=6d66c158e0410fbe57adb8f570f594e7
Positive feedback circuits and adaptive regulations in bacteria.
J Guespin-Michel, M Kaufman.
The mechanisms by which bacteria adapt to changes in their environment involve transcriptional regulation in which a transcriptional regulator responds to signal(s) from the environment and regulates (positively or negatively) the expression of several genes or operons. Some of these regulators exert a positive feedback on their own expression. This is a necessary (although not sufficient) condition for the occurrence of multistationarity. One biological consequence of multistationarity may be epigenetic modifications, a hypothesis unusual to microbiologists, in spite of some well-known epigenetic modifications in bacteria. We propose here that the occurrence of mucoidy in the opportunistic pathogen Pseudomonas aeruginosa, which is currently attributed to mutations only, may also be an epigenetic modification. A theoretical approach using a generalised logical analysis lends credit to this hypothesis and suggests experiments to ascertain it. - Acta biotheoretica (2001) vol. 49 (4) pp. 207-18
http://www.springerlink.com/content/1crxghpx4hgarqql/
Low pH and cold temperature combine to limit growth and pectate lyase production by the psychrotrophic bacterium Erwinia carotovora ssp. carotovora MFCL0.
P Laurent, L Buchon, J Burini, N Orange.
Growth and pectate lyase production by Erwinia carotovora ssp. carotovora MFCL0 were optimal at 28 °C and 14 °C, respectively. Although cold conditions (8 °C ) have retarded bacterial growth, low temperatures were not sufficient to prevent enzyme production but can be combined with a low pH (5.2) to protect vegetables against this phytopathogen. - Biotechnology Letters (2001)
http://www.springerlink.com/index/T228490U18615572.pdf
Isolation and characterisation of the major outer membrane protein of Erwinia carotovora.
C El Hamel, S Chevalier, E Dé, N Orange, Gérard Molle.
The purified major outer membrane protein (37275 Da) from the psychrotrophic phytopathogen Erwinia carotovora MFCL0 was structurally characterised by MALDI-TOF mass spectrometry, N-terminal microsequencing and DNA sequence determinations, and secondary structure prediction analyses. The deduced amino acid sequence showed 76% and 72% of similarities with the Serratia marcescens and Escherichia coli OmpA proteins respectively. Dendrogram analysis allowed to point out that E. carotovora is close to the genus Serratia. After reconstitution into planar lipid bilayers, this major protein induced ion channels with a major conductance level of 630 pS in 1 M NaCl and a weak cationic selectivity. These functional and structural features allowed to identify this major outer membrane component of E. carotovora as an OmpA-like protein, i.e., a channel-forming protein which could be involved in the infection process of this phytopathogen agent. - BBA-Biomembranes (2001) vol. 1515 (1) pp. 12-22
doi: 10.1016/S0005-2736(01)00387-X
http://linkinghub.elsevier.com/retrieve/pii/S000527360100387X
Estimation of the abundance of the cadmium resistance gene cadA in microbial communities in polluted estuary water.
C Oger, T Berthe, L Quillet, S Barray, J F Chiffoleau, F Petit.
We describe herein a molecular method for estimating the abundance of the cadA gene, which encodes a Cd2+/ATPase protein transporter, in bacterial DNA extracted from samples of environmental water. Competitive polymerase chain reaction (cPCR) may be the most appropriate technique for assessing the prevalence of the cadA gene in microbial communities in highly heterogeneous and polluted environments, such as the Seine estuary (France). We describe the development of this method: (i) the choice of two specific primers, based on the sequences encoding the cadmium binding site and the ion channel domains; (ii) the construction of a competitor sequence and assessment of its amplification efficiency; and (iii) the estimation of the copy number of the cadA gene. The cadA content in the bacterial community is expressed as the number of gene copies per ng of total DNA extracted, which is independent of the DNA extraction yield. This molecular procedure was improved to analyze cadA levels in bacterial DNA extracted from estuary water accidentally contaminated with cadmium. Results revealed a subsequent increase in the copy number of the cadA gene in the microbial community. - Research in microbiology (2001) vol. 152 (7) pp. 671-8
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=11605987&dopt=abstractplus
Epigenesis--a request for information on loss of adaptive phenotypes.
J Guespin-Michel.
Microbiology (Reading, England) (2001) vol. 147 (Pt 2) pp. 252-3
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=11158342&dopt=abstractplus
A novel gene from Myxococcus xanthus that facilitates membrane translocation of an extracellular endoglucanase in Escherichia coli?.
L Bensmail, C Monnier, L Quillet, J F Guespin-Michel, S Barray.
Expression in Escherichia coli of the Myxococcus xanthus gene celA, which encodes an extracellular endoglucanase, resulted in CelA being distributed between cytoplasm, periplasm and membrane. The presence of an adjacent open reading frame downstream from the full celA gene, or the absence of a putative lipoprotein signal sequence, confined CelA distribution to the periplasm and membrane, or to the cytoplasm and periplasm, respectively. - Research in microbiology (2001) vol. 152 (5) pp. 487-92
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-436FB18-9&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9cd693105b7e21de51862265650d2cd2
Temperature dependence of extracellular enzymes production by psychrotrophic and psychrophilic bacteria.
L Buchon, P Laurent, A Gounot, J Guespin ….
The effect of different growth temperatures on the production of 11 extracellular enzymes was studied in nine cold-adapted bacterial strains isolated from various cold environments. Ten of these enzymes displayed temperature-dependent production. Five different temperature-related production patterns were identified, which depended on neither the type of strain, nor the nature of the enzyme.
- Biotechnology Letters (2000) vol. 22 (19) pp. 1577-1581
http://www.springerlink.com/index/M138H826140M6506.pdf
Production of pectate lyases and cellulases by Chryseomonas luteola strain MFCL0 depends on the growth temperature and the nature of the culture medium: evidence for two critical temperatures.
P Laurent, L Buchon, J F Guespin-Michel, N Orange.
Several extracellular enzymes that are responsible for plant tissue maceration were detected in culture supernatant of the psychrotrophic bacterium Chryseomonas luteola MFCL0. Isoelectrofocusing experiments showed that pectate lyase (PL) activity resulted from the cumulative action of three major isoenzymes, designated PLI, PLII, and PLIII. Cellulolytic activity was also detected in culture supernatants. These enzymes exhibited different behaviors with respect to growth temperature. PLII was not regulated by temperature, whereas PLI and PLIII were regulated similarly by growth temperature. Maximal levels of PLI and PLIII were produced at 14 degrees C when cells were grown in polygalacturonate-containing synthetic medium and at around 20 to 24 degrees C in nutrient broth. In contrast, thermoregulation of cellulolytic activity production differed from thermoregulation of PL. The level of cellulolytic activity was low in all media at temperatures up to 20 degrees C, and then it increased dramatically until the temperature was 28 degrees C, which is the optimal temperature for growth of C. luteola. Previously, we defined the critical temperature by using the modified Arrhenius equation to characterize bacterial behavior. This approach consists of monitoring changes in the maximal specific growth rate as a function of temperature. Our most striking result was the finding that the temperature at which maximum levels of PLI and PLIII were produced in two different media was the same as the critical temperature for growth observed in these two media. - Applied and environmental microbiology (2000) vol. 66 (4) pp. 1538-43
http://aem.asm.org/cgi/content/full/66/4/1538?view=long&pmid=10742239
Involvement of the C-terminal part of Pseudomonas fluorescens OprF in the modulation of its pore-forming properties.
C El Hamel, M Freulet, M Jaquinod, E De, G Molle, N Orange.
The major outer-membrane protein, OprF, from the psychrotrophic bacterium Pseudomonas fluorescens undergoes a reduction of its conductance value (from 250 pS to 80 pS) when the growth temperature is shifted from 28°C to 8°C. The involvement of changes in tertiary or quaternary structure in this behaviour, was implied by enzymatic digestion experiments in which OprFs purified from 8°C and 28°C cultures showed different accessibility to pronase. Resistant proteolytic fragments of 19 kDa, obtained from both OprF preparations, were identified as the N-terminal half of the native protein. These 19 kDa fragments induced ion channels in planar lipid bilayers with similar conductance values of 65–75 pS in 1 M NaCl, in contrast to the native proteins. Thus, the C-terminal part of the protein is required for the growth temperature-dependent modulation of OprF channel-forming properties. LPS was not detected on the proteolytic fragments while it was found in similar amounts on the native OprFs. These results suggest the LPS/porin association occurs through the C-terminal part of the porin. Radiolabelling experiments showed different phosphorylation levels of LPS for 8°C and 28°C cultures. Thus, in response to growth temperature, the structural modification of the LPS could be associated to the modulation of OprF pore size. - Biochimica et Biophysica Acta - Biomembranes (2000) vol. 1509 (1-2) pp. 237-244
doi: 10.1016/S0005-2736(00)00300-X
http://linkinghub.elsevier.com/retrieve/pii/S000527360000300X
Evidence for association of lipopolysaccharide with Pseudomonas fluorescens strain MF0 porin OprF.
M A Freulet-Marrière, C El Hamel, S Chevalier, E Dé, G Molle, N Orange.
Lipopolysaccharide (LPS) was found to be associated with the major outer membrane protein OprF of the psychrotrophic bacterium Pseudomonas fluorescens MF0, using two OprF purification procedures. OprF, purified under mild conditions, presented two types of association with LPS: tight (tLPS) and slight (sLPS), both of type R. LPS protected OprF from heat modification and trypsin degradation and facilitated the reincorporation of purified OprF into an artificial lipid bilayer without affecting its pore-forming activity. The size of the OprF channel depended on cell growth temperature, as did the extent of LPS phosphorylation: we suggest that LPS may be involved in modifications of OprF pore formation. - Research in microbiology (2000) vol. 151 (10) pp. 873-6
doi: 10.1016/S0923-2508(00)01154-2
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-42BS94X-9&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c4620b7749a144207f991bf4b0e17d44
Effects of high hydrostatic pressure on membrane proteins of Salmonella typhimurium.
M Ritz, M Freulet, N Orange, M Federighi.
Salmonella typhimurium is a leading cause of foodborne diseases. Today high hydrostatic pressure treatments are considered as alternative methods of preservation. To select optimal conditions of treatment, we have to characterize the cell targets of pressure. In this study the action of pressure on the bacterial membrane proteins is analysed. The total membrane extract is obtained by lysis of cells separated by equilibrium density gradient centrifugation. Protein content is analysed by electrophoresis SDS–PAGE and visualised by silver stain. Electrophoretic profiles reveal the presence of three major outer membrane proteins and 12 minor proteins in control bacteria outer membranes. Outer membrane protein content is drastically modified after treatments. In some cases, except for the major proteins OmpA and LamB, other outer membrane proteins seem to totally disappear. LamB is more resistant to hyperbaric exposure when the pH of the media is acidic. This behaviour could be explained by a different conformation adopted by the LamB protein depending on the extracellular pH. This work allows us to define membrane proteins as a target of high hydrostatic pressure treatments. Knowledge of the behaviour of these bacterial membrane proteins subjected to pressure under different conditions (pH, temperature, aw…) could allow an increase in the efficiency of treatments. - International journal of food microbiology (2000)
doi: 10.1016/S0168-1605(00)00165-3
http://linkinghub.elsevier.com/retrieve/pii/S0168160500001653
Characterization of an OprF-deficient mutant suggests that OprF is an essential protein for Pseudomonas fluorescens strain MF0.
S Chevalier, J F Burini, M A Freulet-Marriere, C Regeard, G Schoofs, J Guespin-Michel, R De Mot, N Orange.
A stable OprF-deficient mutant for Pseudomonas fluorescens strain MF0 was constructed using reverse genetics. This mutant, called MF372, showed a rounded morphology and grew more slowly in minimal medium, but not in rich medium. Contrary to other Pseudomonas strains, the loss of OprF for strain MF0 was accompanied by an altered outer membrane composition. At least three outer membrane proteins were overexpressed, apparently as a consequence of adaptive mutations. The N-terminal sequence of two of them revealed strong similarities with porins of the OprD family from P. aeruginosa. The data presented here shows that OprF may be an essential protein for this P. fluorescens strain. - Research in microbiology (2000) vol. 151 (8) pp. 619-27
doi: 10.1016/S0923-2508(00)90128-1
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-41GWN7Y-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3d4fa306cb4ea38726eda7edf7b91660
A bioluminescence assay for screening thermoregulated genes in a psychrotrophic bacterium Pseudomonas fluorescens.
C Regeard, A Mérieau, J F Guespin-Michel.
Random transcription fusion delivery, with bacterial luciferase genes as reporter, was performed in the psychrotrophic bacterium Pseudomonas fluorescens. Direct screening on plates of the insertions allowed the isolation of fusions into thermoregulated genes with good accuracy, either in a library of insertion fusions, or after genetic transfer of a putative regulatory mutation. Using this method, it was shown that in Ps. fluorescens, nearly 40% of the genes are thermoregulated and belong to at least three classes according to the maximal temperature of expression of the fused genes. This is more than had been estimated by a previous method, and demonstrates the importance of thermoregulation in psychrotrophic bacteria. As this reporter is the first to be used for direct screening for genes regulated by temperature, it should be of great value in the study of mechanisms involved in adaptation to this environmental factor. - Journal of applied microbiology (2000) vol. 88 (1) pp. 183-9
http://www3.interscience.wiley.com/journal/119190823/abstract
L Buchon, P Laurent, A Gounot, J Guespin ….
The effect of different growth temperatures on the production of 11 extracellular enzymes was studied in nine cold-adapted bacterial strains isolated from various cold environments. Ten of these enzymes displayed temperature-dependent production. Five different temperature-related production patterns were identified, which depended on neither the type of strain, nor the nature of the enzyme.
- Biotechnology Letters (2000) vol. 22 (19) pp. 1577-1581
http://www.springerlink.com/index/M138H826140M6506.pdf
Production of pectate lyases and cellulases by Chryseomonas luteola strain MFCL0 depends on the growth temperature and the nature of the culture medium: evidence for two critical temperatures.
P Laurent, L Buchon, J F Guespin-Michel, N Orange.
Several extracellular enzymes that are responsible for plant tissue maceration were detected in culture supernatant of the psychrotrophic bacterium Chryseomonas luteola MFCL0. Isoelectrofocusing experiments showed that pectate lyase (PL) activity resulted from the cumulative action of three major isoenzymes, designated PLI, PLII, and PLIII. Cellulolytic activity was also detected in culture supernatants. These enzymes exhibited different behaviors with respect to growth temperature. PLII was not regulated by temperature, whereas PLI and PLIII were regulated similarly by growth temperature. Maximal levels of PLI and PLIII were produced at 14 degrees C when cells were grown in polygalacturonate-containing synthetic medium and at around 20 to 24 degrees C in nutrient broth. In contrast, thermoregulation of cellulolytic activity production differed from thermoregulation of PL. The level of cellulolytic activity was low in all media at temperatures up to 20 degrees C, and then it increased dramatically until the temperature was 28 degrees C, which is the optimal temperature for growth of C. luteola. Previously, we defined the critical temperature by using the modified Arrhenius equation to characterize bacterial behavior. This approach consists of monitoring changes in the maximal specific growth rate as a function of temperature. Our most striking result was the finding that the temperature at which maximum levels of PLI and PLIII were produced in two different media was the same as the critical temperature for growth observed in these two media. - Applied and environmental microbiology (2000) vol. 66 (4) pp. 1538-43
http://aem.asm.org/cgi/content/full/66/4/1538?view=long&pmid=10742239
Involvement of the C-terminal part of Pseudomonas fluorescens OprF in the modulation of its pore-forming properties.
C El Hamel, M Freulet, M Jaquinod, E De, G Molle, N Orange.
The major outer-membrane protein, OprF, from the psychrotrophic bacterium Pseudomonas fluorescens undergoes a reduction of its conductance value (from 250 pS to 80 pS) when the growth temperature is shifted from 28°C to 8°C. The involvement of changes in tertiary or quaternary structure in this behaviour, was implied by enzymatic digestion experiments in which OprFs purified from 8°C and 28°C cultures showed different accessibility to pronase. Resistant proteolytic fragments of 19 kDa, obtained from both OprF preparations, were identified as the N-terminal half of the native protein. These 19 kDa fragments induced ion channels in planar lipid bilayers with similar conductance values of 65–75 pS in 1 M NaCl, in contrast to the native proteins. Thus, the C-terminal part of the protein is required for the growth temperature-dependent modulation of OprF channel-forming properties. LPS was not detected on the proteolytic fragments while it was found in similar amounts on the native OprFs. These results suggest the LPS/porin association occurs through the C-terminal part of the porin. Radiolabelling experiments showed different phosphorylation levels of LPS for 8°C and 28°C cultures. Thus, in response to growth temperature, the structural modification of the LPS could be associated to the modulation of OprF pore size. - Biochimica et Biophysica Acta - Biomembranes (2000) vol. 1509 (1-2) pp. 237-244
doi: 10.1016/S0005-2736(00)00300-X
http://linkinghub.elsevier.com/retrieve/pii/S000527360000300X
Evidence for association of lipopolysaccharide with Pseudomonas fluorescens strain MF0 porin OprF.
M A Freulet-Marrière, C El Hamel, S Chevalier, E Dé, G Molle, N Orange.
Lipopolysaccharide (LPS) was found to be associated with the major outer membrane protein OprF of the psychrotrophic bacterium Pseudomonas fluorescens MF0, using two OprF purification procedures. OprF, purified under mild conditions, presented two types of association with LPS: tight (tLPS) and slight (sLPS), both of type R. LPS protected OprF from heat modification and trypsin degradation and facilitated the reincorporation of purified OprF into an artificial lipid bilayer without affecting its pore-forming activity. The size of the OprF channel depended on cell growth temperature, as did the extent of LPS phosphorylation: we suggest that LPS may be involved in modifications of OprF pore formation. - Research in microbiology (2000) vol. 151 (10) pp. 873-6
doi: 10.1016/S0923-2508(00)01154-2
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-42BS94X-9&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c4620b7749a144207f991bf4b0e17d44
Effects of high hydrostatic pressure on membrane proteins of Salmonella typhimurium.
M Ritz, M Freulet, N Orange, M Federighi.
Salmonella typhimurium is a leading cause of foodborne diseases. Today high hydrostatic pressure treatments are considered as alternative methods of preservation. To select optimal conditions of treatment, we have to characterize the cell targets of pressure. In this study the action of pressure on the bacterial membrane proteins is analysed. The total membrane extract is obtained by lysis of cells separated by equilibrium density gradient centrifugation. Protein content is analysed by electrophoresis SDS–PAGE and visualised by silver stain. Electrophoretic profiles reveal the presence of three major outer membrane proteins and 12 minor proteins in control bacteria outer membranes. Outer membrane protein content is drastically modified after treatments. In some cases, except for the major proteins OmpA and LamB, other outer membrane proteins seem to totally disappear. LamB is more resistant to hyperbaric exposure when the pH of the media is acidic. This behaviour could be explained by a different conformation adopted by the LamB protein depending on the extracellular pH. This work allows us to define membrane proteins as a target of high hydrostatic pressure treatments. Knowledge of the behaviour of these bacterial membrane proteins subjected to pressure under different conditions (pH, temperature, aw…) could allow an increase in the efficiency of treatments. - International journal of food microbiology (2000)
doi: 10.1016/S0168-1605(00)00165-3
http://linkinghub.elsevier.com/retrieve/pii/S0168160500001653
Characterization of an OprF-deficient mutant suggests that OprF is an essential protein for Pseudomonas fluorescens strain MF0.
S Chevalier, J F Burini, M A Freulet-Marriere, C Regeard, G Schoofs, J Guespin-Michel, R De Mot, N Orange.
A stable OprF-deficient mutant for Pseudomonas fluorescens strain MF0 was constructed using reverse genetics. This mutant, called MF372, showed a rounded morphology and grew more slowly in minimal medium, but not in rich medium. Contrary to other Pseudomonas strains, the loss of OprF for strain MF0 was accompanied by an altered outer membrane composition. At least three outer membrane proteins were overexpressed, apparently as a consequence of adaptive mutations. The N-terminal sequence of two of them revealed strong similarities with porins of the OprD family from P. aeruginosa. The data presented here shows that OprF may be an essential protein for this P. fluorescens strain. - Research in microbiology (2000) vol. 151 (8) pp. 619-27
doi: 10.1016/S0923-2508(00)90128-1
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-41GWN7Y-3&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=3d4fa306cb4ea38726eda7edf7b91660
A bioluminescence assay for screening thermoregulated genes in a psychrotrophic bacterium Pseudomonas fluorescens.
C Regeard, A Mérieau, J F Guespin-Michel.
Random transcription fusion delivery, with bacterial luciferase genes as reporter, was performed in the psychrotrophic bacterium Pseudomonas fluorescens. Direct screening on plates of the insertions allowed the isolation of fusions into thermoregulated genes with good accuracy, either in a library of insertion fusions, or after genetic transfer of a putative regulatory mutation. Using this method, it was shown that in Ps. fluorescens, nearly 40% of the genes are thermoregulated and belong to at least three classes according to the maximal temperature of expression of the fused genes. This is more than had been estimated by a previous method, and demonstrates the importance of thermoregulation in psychrotrophic bacteria. As this reporter is the first to be used for direct screening for genes regulated by temperature, it should be of great value in the study of mechanisms involved in adaptation to this environmental factor. - Journal of applied microbiology (2000) vol. 88 (1) pp. 183-9
http://www3.interscience.wiley.com/journal/119190823/abstract
Nucleic acid extraction from polluted estuarine water for detection of viruses and bacteria by PCR and RT-PCR analysis.
F Petit, S Craquelin, J Guespin-Michel, C Buffet-Janvresse.
We describe an extraction protocol for genomic DNA and RNA of both viruses and bacteria from polluted estuary water. This procedure was adapted to the molecular study of microflora of estuarine water where bacteria and viruses are found free, forming low-density biofilms, or intimately associated with organo-mineral particles. The sensitivity of the method was determined with seeded samples for RT-PCR and PCR analysis of viruses (10 virions/mL), and bacteria (1 colony-forming unit mL). We report an example of molecular detection of both poliovirus and Salmonella in the Seine estuary (France) and an approach to studying their association with organo-mineral particles. - Research in microbiology (1999) vol. 150 (2) pp. 143-51
doi: 10.1016/S0923-2508(99)80031-X
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-3WWCK27-G&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=68c07890387a59f419a1b143ef3f5860
Genetic studies of a thermoregulated gene in the psychrotrophic bacterium Pseudomonas fluorescens.
C Regeard, A Mérieau, F Leriche, J F Guespin-Michel.
In the psychrotrophic bacterium Pseudomonas fluorescens, some genes are thermoregulated: they are maximally expressed at a particular temperature within the broad range of temperatures that allow growth of this bacterium. To study this regulation, random transcriptional insertion fusions were obtained by means of mini-Tn5lacZ1 or mini-Tn5luxAB transposition. One fusion was studied in which beta-galactosidase production was maximal at a low-growth temperature. The mutated gene (that we call xsf) was highly homologous to xseA from Escherichia coli (and from other bacteria) which encodes the large subunit of exonuclease VII. Genetic tools were constructed in order to analyse and manipulate this fusion: a plasmid derived from R68.45 was used for chromosome transfer and a replacement vector was constructed to allow in situ marker exchange of the mini-Tn5lacZ1 by an Hg(r) interposon. This vector was used to make double mutants and hence to study the effect of the insertion in xsf on the expression of other fusions. Six genes were thereby identified with a decreased expression in an xsf- background and with different characteristics of thermoregulation. - Research in microbiology (1999) vol. 150 (7) pp. 447-56
doi:10.1016/S0923-2508(99)00112-6
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-402TNX2-9&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c742d85b765e00d0762c7f90794f910e
F Petit, S Craquelin, J Guespin-Michel, C Buffet-Janvresse.
We describe an extraction protocol for genomic DNA and RNA of both viruses and bacteria from polluted estuary water. This procedure was adapted to the molecular study of microflora of estuarine water where bacteria and viruses are found free, forming low-density biofilms, or intimately associated with organo-mineral particles. The sensitivity of the method was determined with seeded samples for RT-PCR and PCR analysis of viruses (10 virions/mL), and bacteria (1 colony-forming unit mL). We report an example of molecular detection of both poliovirus and Salmonella in the Seine estuary (France) and an approach to studying their association with organo-mineral particles. - Research in microbiology (1999) vol. 150 (2) pp. 143-51
doi: 10.1016/S0923-2508(99)80031-X
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-3WWCK27-G&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=68c07890387a59f419a1b143ef3f5860
Genetic studies of a thermoregulated gene in the psychrotrophic bacterium Pseudomonas fluorescens.
C Regeard, A Mérieau, F Leriche, J F Guespin-Michel.
In the psychrotrophic bacterium Pseudomonas fluorescens, some genes are thermoregulated: they are maximally expressed at a particular temperature within the broad range of temperatures that allow growth of this bacterium. To study this regulation, random transcriptional insertion fusions were obtained by means of mini-Tn5lacZ1 or mini-Tn5luxAB transposition. One fusion was studied in which beta-galactosidase production was maximal at a low-growth temperature. The mutated gene (that we call xsf) was highly homologous to xseA from Escherichia coli (and from other bacteria) which encodes the large subunit of exonuclease VII. Genetic tools were constructed in order to analyse and manipulate this fusion: a plasmid derived from R68.45 was used for chromosome transfer and a replacement vector was constructed to allow in situ marker exchange of the mini-Tn5lacZ1 by an Hg(r) interposon. This vector was used to make double mutants and hence to study the effect of the insertion in xsf on the expression of other fusions. Six genes were thereby identified with a decreased expression in an xsf- background and with different characteristics of thermoregulation. - Research in microbiology (1999) vol. 150 (7) pp. 447-56
doi:10.1016/S0923-2508(99)00112-6
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-402TNX2-9&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=c742d85b765e00d0762c7f90794f910e
Defining integrative biology.
Ripoll, J Guespin-Michel, V Norris, M Thellier.
Complexity (1998) vol. Volume 4 (2) pp. 19-20
http://www3.interscience.wiley.com/journal/40000383/abstract
Regulation of the expression of a gene encoding beta-endoglucanase secreted by Myxococcus xanthus during growth: role of genes involved in developmental regulation.
L Bensmail, L Quillet, F Petit, S Barray, J F Guespin-Michel.
An endoglucanase, CelA, is secreted by Myxococcus xanthus only during exponential growth. The production of this enzyme is decreased by mutations in 5 different genes (Exc +/- phenotype), three of which correspond to asg genes which regulate the production of an early cell-to-cell signal in development. Transcription of celA is decreased in two of these Exc +/- mutants, whereas a post-transcriptional step is affected in two other Exc- mutants. Thus, asg genes, in addition to regulating the onset of development, also regulate a gene (celA) that is expressed during exponential growth and that is not involved in development. - Research in microbiology (1998) vol. 149 (5) pp. 319-26
doi::10.1016/S0923-2508(98)80437-3
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-3V482X1-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0b60e32dda78e5e5dd5768eb481b1674
Ripoll, J Guespin-Michel, V Norris, M Thellier.
Complexity (1998) vol. Volume 4 (2) pp. 19-20
http://www3.interscience.wiley.com/journal/40000383/abstract
Regulation of the expression of a gene encoding beta-endoglucanase secreted by Myxococcus xanthus during growth: role of genes involved in developmental regulation.
L Bensmail, L Quillet, F Petit, S Barray, J F Guespin-Michel.
An endoglucanase, CelA, is secreted by Myxococcus xanthus only during exponential growth. The production of this enzyme is decreased by mutations in 5 different genes (Exc +/- phenotype), three of which correspond to asg genes which regulate the production of an early cell-to-cell signal in development. Transcription of celA is decreased in two of these Exc +/- mutants, whereas a post-transcriptional step is affected in two other Exc- mutants. Thus, asg genes, in addition to regulating the onset of development, also regulate a gene (celA) that is expressed during exponential growth and that is not involved in development. - Research in microbiology (1998) vol. 149 (5) pp. 319-26
doi::10.1016/S0923-2508(98)80437-3
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VN3-3V482X1-2&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=0b60e32dda78e5e5dd5768eb481b1674
Growth temperature dependence of channel size of the major outer-membrane protein (OprF) in psychrotrophic Pseudomonas fluorescens strains.
E Dé, N Orange, N Saint, J Guérillon, R De Mot, G Molle.
The outer-membrane (OM) permeability of the psychrotrophic bacterium Pseudomonas fluorescens strain MF0 for the beta-lactam mezlocillin is increased at the optimum growth temperature (28 degrees C) compared to low growth temperatures (8 degrees C). In an attempt to explain this phenomenon, OM protein content was studied in cultures grown at both temperatures. No significant difference in proportion or composition was found, suggesting that a change in the structure and function of porins could be responsible for the differential permeability. The major OM protein OprF of two psychrotrophic P. fluorescens strains, MF0 and OE 28.3, was purified from cultures grown at 8 degrees C and 28 degrees C in order to reincorporate them in solvent-free lipid bilayers. From cultures grown at the same temperature, OprF displayed very similar channel-forming properties for both strains. Decreasing the growth temperature induced a threefold reduction of the major conductance values (250-270 pS in 1 M NaCl for 28 degrees C cultures and 80-90 pS in 1 M NaCl for 8 degrees C cultures). The trypsin digestion kinetics showed a very different reactivity for these porins between cultures grown at 8 degrees C and 28 degrees C. This may indicate that the pore structure of OprF is modified depending on the growth temperature, as suggested by its functional behaviour. - Microbiology (Reading, England) (1997) vol. 143 ( Pt 3) pp. 1029-35
http://mic.sgmjournals.org/cgi/pmidlookup?view=reprint&pmid=9084185
A gene involved in both protein secretion during growth and starvation-induced development encodes a subunit of the NADH:ubiquinone oxidoreductase in Myxococcus xanthus.
K Laval-Favre, B Letouvet-Pawlak, T Friedrich, J Alexandre, J F Guespin-Michel.
The secretion of numerous proteins during vegetative growth of Myxococcus xanthus, and the multicellular development cycle induced upon starvation of these bacteria, are partially interrelated in so far as mutants impaired in extracellular protein production are unable to undergo development. We have cloned and sequenced a gene in which a Tn5 insertion leads to a decrease in the production of most, if not all, extracellular proteins, and prevents development and sporulation. The deduced protein is homologous to the putative ubiquinone-binding subunit of bacterial and mitochondrial NADH:ubiquinone oxidoreductases (complex I). This is the first example of the presence of this complex in a bacterium from subclass delta of the proteobacteria. This gene is expressed during growth and during early development. As its disruption by Tn5 does not impair growth of the mutant strain, we assume the presence of a second alternative NADH oxidoreductase, and suggest that the phenotypic alterations caused by the mutation are due to a decrease in the proton-motive force. - Molecular Microbiology (1997) vol. 23 (5) pp. 1043-52
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=9076740&dopt=abstractplus
Cloning and sequencing of two genes, prtA and prtB, from Myxococcus xanthus, encoding PrtA and PrtB proteases, both of which are required for the protease activity.
L Quillet, L Bensmail, S Barray, J Guespin-Michel.
The sequence of a 1955-bp TaqI DNA fragment from Myxococcus xanthus was determined. This fragment contains two complete genes, designated prtA and prtB. The prtA and prtB ORFs extend over 828 and 798 bp, respectively. They are separated only by 3 nt and appear to be present in a polycistronic transcriptional unit. A typical lipoprotein signal sequence is present at the N terminus of the two deduced polypeptides. The aa sequence of PrtA shows a high degree of identity to the region adjacent to the Ser residue belonging to the catalytic triad of serine proteases from Staphylococcus aureus and Enterococcus faecalis. It also exhibits features characteristic of trypsin-like serine proteases in that it contains the same pattern of variable and conserved regions. The deduced aa sequence of PrtB reveals a signature zinc-binding consensus motif (HEXXHXXGXXH/Met-turn) characteristic of the class of metalloproteases called metzincins. Plasmids containing prtA, prtB, or both were constructed. Protease activity studies of Escherichia coli clones containing these plasmids showed that both genes are necessary for this activity, whatever their cis or trans position. As prtB produces a putative membrane-bound lipoprotein of 266 aa, the protease activation must occur at the membrane level. - Gene (1997) vol. 198 (1-2) pp. 135-40
doi= 10.1016/S0378-1119(97)00303-X
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T39-3VBSRC2-K&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=db394109dc0d16f955ff30ff59ccf9b4
Isolation of a soil psychrotrophic toluene-degrading Pseudomonas strain: influence of temperature on the growth characteristics on different substrates.
P Chablain, G Philippe, A Groboillot, Truffaut, JF Guespin-Michel.
Two psychrotrophic toluene-degrading Pseudomonas putida strains were isolated at low temperature from a toluene-polluted soil, thereby demonstrating that toluene degradation at low temperature occurred in nature, a finding of possible interest for soil bioremediation procedures. In one of these strains, two aromatic compounds (toluene and benzoate) were degraded, most likely through different pathways. To study the effect of the growth temperature on the metabolism of these substrates, we studied the evolution of the maximal growth rates with respect to both temperature and substrate. It was shown that not only cardinal temperatures but also temperature characteristics deduced from the Arrhenius plot of maximal growth rates differed when the different substrates were used as sole carbon and energy source. -Research in microbiology (1997) vol. 148 (2) pp. 153-161
http://linkinghub.elsevier.com/retrieve/pii/S0923250897876462
E Dé, N Orange, N Saint, J Guérillon, R De Mot, G Molle.
The outer-membrane (OM) permeability of the psychrotrophic bacterium Pseudomonas fluorescens strain MF0 for the beta-lactam mezlocillin is increased at the optimum growth temperature (28 degrees C) compared to low growth temperatures (8 degrees C). In an attempt to explain this phenomenon, OM protein content was studied in cultures grown at both temperatures. No significant difference in proportion or composition was found, suggesting that a change in the structure and function of porins could be responsible for the differential permeability. The major OM protein OprF of two psychrotrophic P. fluorescens strains, MF0 and OE 28.3, was purified from cultures grown at 8 degrees C and 28 degrees C in order to reincorporate them in solvent-free lipid bilayers. From cultures grown at the same temperature, OprF displayed very similar channel-forming properties for both strains. Decreasing the growth temperature induced a threefold reduction of the major conductance values (250-270 pS in 1 M NaCl for 28 degrees C cultures and 80-90 pS in 1 M NaCl for 8 degrees C cultures). The trypsin digestion kinetics showed a very different reactivity for these porins between cultures grown at 8 degrees C and 28 degrees C. This may indicate that the pore structure of OprF is modified depending on the growth temperature, as suggested by its functional behaviour. - Microbiology (Reading, England) (1997) vol. 143 ( Pt 3) pp. 1029-35
http://mic.sgmjournals.org/cgi/pmidlookup?view=reprint&pmid=9084185
A gene involved in both protein secretion during growth and starvation-induced development encodes a subunit of the NADH:ubiquinone oxidoreductase in Myxococcus xanthus.
K Laval-Favre, B Letouvet-Pawlak, T Friedrich, J Alexandre, J F Guespin-Michel.
The secretion of numerous proteins during vegetative growth of Myxococcus xanthus, and the multicellular development cycle induced upon starvation of these bacteria, are partially interrelated in so far as mutants impaired in extracellular protein production are unable to undergo development. We have cloned and sequenced a gene in which a Tn5 insertion leads to a decrease in the production of most, if not all, extracellular proteins, and prevents development and sporulation. The deduced protein is homologous to the putative ubiquinone-binding subunit of bacterial and mitochondrial NADH:ubiquinone oxidoreductases (complex I). This is the first example of the presence of this complex in a bacterium from subclass delta of the proteobacteria. This gene is expressed during growth and during early development. As its disruption by Tn5 does not impair growth of the mutant strain, we assume the presence of a second alternative NADH oxidoreductase, and suggest that the phenotypic alterations caused by the mutation are due to a decrease in the proton-motive force. - Molecular Microbiology (1997) vol. 23 (5) pp. 1043-52
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=9076740&dopt=abstractplus
Cloning and sequencing of two genes, prtA and prtB, from Myxococcus xanthus, encoding PrtA and PrtB proteases, both of which are required for the protease activity.
L Quillet, L Bensmail, S Barray, J Guespin-Michel.
The sequence of a 1955-bp TaqI DNA fragment from Myxococcus xanthus was determined. This fragment contains two complete genes, designated prtA and prtB. The prtA and prtB ORFs extend over 828 and 798 bp, respectively. They are separated only by 3 nt and appear to be present in a polycistronic transcriptional unit. A typical lipoprotein signal sequence is present at the N terminus of the two deduced polypeptides. The aa sequence of PrtA shows a high degree of identity to the region adjacent to the Ser residue belonging to the catalytic triad of serine proteases from Staphylococcus aureus and Enterococcus faecalis. It also exhibits features characteristic of trypsin-like serine proteases in that it contains the same pattern of variable and conserved regions. The deduced aa sequence of PrtB reveals a signature zinc-binding consensus motif (HEXXHXXGXXH/Met-turn) characteristic of the class of metalloproteases called metzincins. Plasmids containing prtA, prtB, or both were constructed. Protease activity studies of Escherichia coli clones containing these plasmids showed that both genes are necessary for this activity, whatever their cis or trans position. As prtB produces a putative membrane-bound lipoprotein of 266 aa, the protease activation must occur at the membrane level. - Gene (1997) vol. 198 (1-2) pp. 135-40
doi= 10.1016/S0378-1119(97)00303-X
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T39-3VBSRC2-K&_user=10&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=db394109dc0d16f955ff30ff59ccf9b4
Isolation of a soil psychrotrophic toluene-degrading Pseudomonas strain: influence of temperature on the growth characteristics on different substrates.
P Chablain, G Philippe, A Groboillot, Truffaut, JF Guespin-Michel.
Two psychrotrophic toluene-degrading Pseudomonas putida strains were isolated at low temperature from a toluene-polluted soil, thereby demonstrating that toluene degradation at low temperature occurred in nature, a finding of possible interest for soil bioremediation procedures. In one of these strains, two aromatic compounds (toluene and benzoate) were degraded, most likely through different pathways. To study the effect of the growth temperature on the metabolism of these substrates, we studied the evolution of the maximal growth rates with respect to both temperature and substrate. It was shown that not only cardinal temperatures but also temperature characteristics deduced from the Arrhenius plot of maximal growth rates differed when the different substrates were used as sole carbon and energy source. -Research in microbiology (1997) vol. 148 (2) pp. 153-161
http://linkinghub.elsevier.com/retrieve/pii/S0923250897876462
Evidence for two domains of growth temperature for the psychrotrophic bacterium Pseudomonas fluorescens MF0.
C Guillou, J F Guespin-Michel.
The variations in the maximal specific growth rate of the psychrotrophic bacterium Pseudomonas fluorescens MF0 with respect to temperature were studied between 0 and 30 degrees C (optimal for growth). The Arrhenius plot showed a drastic change in slope at the intermediate temperature of 17 degrees C. Over the cold domain from 0 to 17 degrees C, the temperature characteristic was twofold higher than over the suboptimal domain from 17 to 30 degrees C. The macromolecular composition of exponentially growing cells was invariant over the entire range from 0 to 30 degrees C. Variations of temperature and growth rate were independently investigated through chemostat experiments in order to characterize their respective effects on cell macromolecular composition and size. The effect of growth rate in this psychrotrophic strain is identical to that of all other bacteria assayed so far. In contrast, an original biphasic variation of total protein concentration was demonstrated in strain MF0 with respect to temperature, with a maximum at 17 to 20 degrees C. Indeed, increasing the temperature in the chemostat resulted in a biphasic decrease in the net protein production rate: a very slight decrease below 17 degrees C and a much larger decrease from 17 to 28 degrees C. These results could signify an increase in the cellular protein degradation rate with increasing temperature, especially above 17 degrees C. - Applied and environmental microbiology (1996) vol. 62 (9) pp. 3319-24
http://aem.asm.org/cgi/reprint/62/9/3319?view=long&pmid=8795221
C Guillou, J F Guespin-Michel.
The variations in the maximal specific growth rate of the psychrotrophic bacterium Pseudomonas fluorescens MF0 with respect to temperature were studied between 0 and 30 degrees C (optimal for growth). The Arrhenius plot showed a drastic change in slope at the intermediate temperature of 17 degrees C. Over the cold domain from 0 to 17 degrees C, the temperature characteristic was twofold higher than over the suboptimal domain from 17 to 30 degrees C. The macromolecular composition of exponentially growing cells was invariant over the entire range from 0 to 30 degrees C. Variations of temperature and growth rate were independently investigated through chemostat experiments in order to characterize their respective effects on cell macromolecular composition and size. The effect of growth rate in this psychrotrophic strain is identical to that of all other bacteria assayed so far. In contrast, an original biphasic variation of total protein concentration was demonstrated in strain MF0 with respect to temperature, with a maximum at 17 to 20 degrees C. Indeed, increasing the temperature in the chemostat resulted in a biphasic decrease in the net protein production rate: a very slight decrease below 17 degrees C and a much larger decrease from 17 to 28 degrees C. These results could signify an increase in the cellular protein degradation rate with increasing temperature, especially above 17 degrees C. - Applied and environmental microbiology (1996) vol. 62 (9) pp. 3319-24
http://aem.asm.org/cgi/reprint/62/9/3319?view=long&pmid=8795221
Lipase and acidic phosphatase from the psychrotrophic bacterium Pseudomonas fluorescens: two enzymes whose synthesis is regulated by the growth temperature.
J F Burini, B Gügi, A Merieau, J F Guespin-Michel.
In the psychrotrophic bacterium Pseudomonas fluorescens, the production of several enzymes that otherwise differ in their cell location, growth phase production and inducibility appeared to be similarly regulated by the growth temperature. In order to determine the level of this regulation, the expression of the apo and lip genes encoding two of these enzymes, the acidic phosphatase and lipase, respectively, was studied at different temperatures. Both genes were optimally expressed at 17.5 degrees C, i.e., at the optimal temperature of production of the enzymes; however, the low level of activity at the highest temperature could be due to an additional post-transcriptional control. - FEMS microbiology letters (1994) vol. 122 (1-2) pp. 13-8
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=7958764&dopt=abstractplus
J F Burini, B Gügi, A Merieau, J F Guespin-Michel.
In the psychrotrophic bacterium Pseudomonas fluorescens, the production of several enzymes that otherwise differ in their cell location, growth phase production and inducibility appeared to be similarly regulated by the growth temperature. In order to determine the level of this regulation, the expression of the apo and lip genes encoding two of these enzymes, the acidic phosphatase and lipase, respectively, was studied at different temperatures. Both genes were optimally expressed at 17.5 degrees C, i.e., at the optimal temperature of production of the enzymes; however, the low level of activity at the highest temperature could be due to an additional post-transcriptional control. - FEMS microbiology letters (1994) vol. 122 (1-2) pp. 13-8
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=7958764&dopt=abstractplus
Growth temperature controls the production of a single extracellular protease by Pseudomonas fluorescens MF0, in the presence of various inducers.
F C Hellio, N Orange, J F Guespin-Michel.
The psychotrophic strain Pseudomonas fluorescens MFO is known to express several enzymatic activities in milk, including extracellular proteolytic activity, optimally when cells are grown at 17.5 degrees C. In order to study the nature of the mechanisms controlling the production of the extracellular protease, we devised a defined medium in which this enzymatic activity was induced by an amino acid and small peptides. Regardless of the inducer, optimal proteolytic activity appeared at 17.5 degrees C. SDS-PAGE and isoelectrofocussing revealed a single protease produced by P. fluorescens MFO with all the inducers used and at all temperatures examined. The level of proteolytic activity correlated with the amount of enzyme in the supernatants. - Research in microbiology (1993) vol. 144 (8) pp. 617-25
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=8140280&dopt=abstractplus
F C Hellio, N Orange, J F Guespin-Michel.
The psychotrophic strain Pseudomonas fluorescens MFO is known to express several enzymatic activities in milk, including extracellular proteolytic activity, optimally when cells are grown at 17.5 degrees C. In order to study the nature of the mechanisms controlling the production of the extracellular protease, we devised a defined medium in which this enzymatic activity was induced by an amino acid and small peptides. Regardless of the inducer, optimal proteolytic activity appeared at 17.5 degrees C. SDS-PAGE and isoelectrofocussing revealed a single protease produced by P. fluorescens MFO with all the inducers used and at all temperatures examined. The level of proteolytic activity correlated with the amount of enzyme in the supernatants. - Research in microbiology (1993) vol. 144 (8) pp. 617-25
http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=Retrieve&list_uids=8140280&dopt=abstractplus
