Outer membrane Modifications of <i>Pseudomonas fluorescens</i> MF37 in Response to Hyperosmolarity

Guyard‐Nicodème, Muriel; Bazire, Alexis; Hémery, Gaëlle; Meylheuc, Thierry; Mollé, Daniel; Orange, Nicole; Fito-Boncompte, Laurène; Feuilloley, Marc; Haras, Dominique; Dufour, Alain; Chevalier, Sylvie

doi:10.1021/pr070539x

Cited by 41 publications

(36 citation statements)

References 73 publications

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“…The fact that at least half of the porinencoding genes and most of the outer membrane protein-encoding genes were not altered by an osmotic upshift in the two P. syringae strains supports a directed effect on a few porins, potentially reducing permeability to specific molecules, rather than a nonspecific effect on outer membrane proteins due to osmoinduced membrane perturbations. Similar to the porins, osmotic stress did not alter flagellar gene expression in P. aeruginosa cells (39) but reduced the expression and protein levels of the flagellar subunit FliC and reduced the motility of P. fluorescens cells (50). Whereas osmotic stress reduced many flagellar gene transcripts in P. syringae (see Table S2) and matric stress reduced at least flgC and fliE in P. putida (51), suggesting reduced motility of pseudomonads in response to water stress, osmotic stress did not affect flagellar gene transcripts in Desulfovibrio vulgaris (52), indicating that this is not a generalized bacterial response to water limitation.…”

Section: Discussionmentioning

confidence: 87%

“…Although osmotic stress did not alter porin gene expression in P. aeruginosa cells (39), it decreased the levels of porin protein in P. fluorescens (50), including three proteins encoded by genes that were downregulated in B728a and DC3000, OprD, OprE, and OprQ (see Table S2 in the supplemental material). The fact that at least half of the porinencoding genes and most of the outer membrane protein-encoding genes were not altered by an osmotic upshift in the two P. syringae strains supports a directed effect on a few porins, potentially reducing permeability to specific molecules, rather than a nonspecific effect on outer membrane proteins due to osmoinduced membrane perturbations.…”

Section: Discussionmentioning

confidence: 99%

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Physiological and Transcriptional Responses to Osmotic Stress of Two Pseudomonas syringae Strains That Differ in Epiphytic Fitness and Osmotolerance

Freeman

Chen

et al. 2013

J Bacteriol

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The foliar pathogen Pseudomonas syringae is a useful model for understanding the role of stress adaptation in leaf colonization. We investigated the mechanistic basis of differences in the osmotolerance of two P. syringae strains, B728a and DC3000. Consistent with its higher survival rates following inoculation onto leaves, B728a exhibited superior osmotolerance over DC3000 and higher rates of uptake of plant-derived osmoprotective compounds. A global transcriptome analysis of B728a and DC3000 following an osmotic upshift demonstrated markedly distinct responses between the strains; B728a showed primarily upregulation of genes, including components of the type VI secretion system (T6SS) and alginate biosynthetic pathways, whereas DC3000 showed no change or repression of orthologous genes, including downregulation of the T3SS. DC3000 uniquely exhibited improved growth upon deletion of the biosynthetic genes for the compatible solute N-acetylglutaminylglutamine amide (NAGGN) in a minimal medium, due possibly to NAGGN synthesis depleting the cellular glutamine pool. Both strains showed osmoreduction of glnA1 expression, suggesting that decreased glutamine synthetase activity contributes to glutamate accumulation as a compatible solute, and both strains showed osmoinduction of 5 of 12 predicted hydrophilins. Collectively, our results demonstrate that the superior epiphytic competence of B728a is consistent with its strong osmotolerance, a proactive response to an osmotic upshift, osmoinduction of alginate synthesis and the T6SS, and resiliency of the T3SS to water limitation, suggesting sustained T3SS expression under the water-limited conditions encountered during leaf colonization.

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Section: Discussionmentioning

confidence: 87%

Section: Discussionmentioning

confidence: 99%

Physiological and Transcriptional Responses to Osmotic Stress of Two Pseudomonas syringae Strains That Differ in Epiphytic Fitness and Osmotolerance

Freeman

Chen

et al. 2013

J Bacteriol

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“…Extraction of RNAs was performed as previously described by Guyard-Nicodème et al (21). Synthesis of cDNAs and PCR amplification of the oprD gene were achieved with 50 ng of total RNAs by using the Transcriptor One-Step RT-PCR kit (Roche, Mannheim, Germany) with the forward primer 5=-ATCGTAAGCTGAACCAT CGTT-3= and the reverse primer 5=-TCATTTCTGCGGCAATAATTT-3= and following the manufacturer's instructions.…”

Section: Methodsmentioning

confidence: 99%

Deciphering the Function of the Outer Membrane Protein OprD Homologue of Acinetobacter baumannii

Catel-Ferreira

Nehmé

Molle

et al. 2012

Antimicrob Agents Chemother

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ABSTRACTThe increasing number of carbapenem-resistantAcinetobacter baumanniiisolates is a major cause for concern which restricts therapeutic options to treat severe infections caused by this emerging pathogen. To identify the molecular mechanisms involved in carbapenem resistance, we studied the contribution of an outer membrane protein homologue of thePseudomonas aeruginosaOprD porin. Suspected to be the preferred pathway of carbapenems inA. baumannii, theoprDhomologue gene was inactivated in strain ATCC 17978. Comparison of wild-type and mutant strains did not confirm the expected increased resistance to any antibiotic tested. OprD homologue sequence analysis revealed that this protein actually belongs to an OprD subgroup but is closer to theP. aeruginosaOprQ protein, with which it could share some functions, e.g., allowing bacterial survival under low-iron or -magnesium growth conditions or under poor oxygenation. We thus overexpressed and purified a recombinant OprD homologue protein to further examine its functional properties. As a specific channel, this porin presented rather low single-channel conductance, i.e., 28 pS in 1 M KCl, and was partially closed by micro- and millimolar concentrations of Fe3+and Mg2+, respectively, but not by imipenem and meropenem or basic amino acids. TheA. baumanniiOprD homologue is likely not involved in the carbapenem resistance mechanism, but as an OprQ-like protein, it could contribute to the adaptation of this bacterium to magnesium- and/or iron-depleted environments.

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“…qRT-PCR experiments. Quantitative reverse transcription-PCR (qRT-PCR) experiments were conducted as previously described by Guyard-Nicodème et al (25).…”

Section: Fig 1 Schematic Representation Of the Promoter Regions Of Opmentioning

confidence: 99%

Transcription of the oprF Gene of Pseudomonas aeruginosa Is Dependent Mainly on the SigX Sigma Factor and Is Sucrose Induced

et al. 2012

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The OprF porin is the major outer membrane protein of Pseudomonas aeruginosa. OprF is involved in several crucial functions, including cell structure, outer membrane permeability, environmental sensing, and virulence. The oprF gene is preceded by the sigX gene, which encodes the poorly studied extracytoplasmic function (ECF) sigma factor SigX. Three oprF promoters were previously identified. Two intertwined promoters dependent on 70 and SigX are located in the sigX-oprF intergenic region, whereas a promoter dependent on the ECF AlgU lies within the sigX gene. An additional promoter was found in the cmpX-sigX intergenic region. In this study, we dissected the contribution of each promoter region and of each sigma factor to oprF transcription using transcriptional fusions. In Luria-Bertani (LB) medium, the oprF-proximal region (sigX-oprF intergenic region) accounted for about 80% of the oprF transcription, whereas the AlgU-dependent promoter had marginal activity. Using the sigX mutant PAOSX, we observed that the SigX-dependent promoter was largely predominant over the 70 -dependent promoter. oprF transcription was increased in response to low NaCl or high sucrose concentrations, and this induced transcription was strongly impaired in the absence of SigX. The lack of OprF itself increased oprF transcription. Since these conditions led to cell wall alterations, oprF transcription could be activated by signals triggered by perturbation of the cell envelope.

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Outer membrane Modifications of Pseudomonas fluorescens MF37 in Response to Hyperosmolarity

Cited by 41 publications

References 73 publications

Physiological and Transcriptional Responses to Osmotic Stress of Two Pseudomonas syringae Strains That Differ in Epiphytic Fitness and Osmotolerance

Physiological and Transcriptional Responses to Osmotic Stress of Two Pseudomonas syringae Strains That Differ in Epiphytic Fitness and Osmotolerance

Deciphering the Function of the Outer Membrane Protein OprD Homologue of Acinetobacter baumannii

Transcription of the oprF Gene of Pseudomonas aeruginosa Is Dependent Mainly on the SigX Sigma Factor and Is Sucrose Induced

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