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The minimum low-salt stimulon in Vibrio parahaemolyticus

ABSTRACT: Global gene expression profiles of V. parahaemolyticus grown under 2% and 0.66% NaCl were compared to define the minimum low-salt stimulon. The ectABC-lysC operon for synthesis of the compatible solute ectoine, as well as three compatible-solute transport systems, namely ProU (glycine betaine), OpuD1 (glycine betaine) and Pot2 (spermidine), was up-regulated under 2% NaCl in relative to 0.66% NaCl. The 2% NaCl condition favored the inducible expression of OmpW, OmpN and OmpA2, while repressed the expression of OmpA1, OmpU and VP1008. These results indicated that, to master the hyperosmotic stress of saline environments, V. parahaemolyticus might not only accumulate osmoprotectants through uptake or endogenous synthesis of compatible solutes, but also remodel its profiles of outer membrane protein to restore its cell membrane. The above differentially regulated genes will provide novel candidates for the further investigation of the molecular mechanisms of osmoadaptation in V. parahaemolyticus.

ORGANISM(S): Vibrio parahaemolyticus

PROVIDER: GSE16530 | GEO | 2009/07/07

SECONDARY ACCESSION(S): PRJNA116097

REPOSITORIES: GEO

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Project description:Quantitative RNA sequencing (RNA-seq) and the complementary phenotypic assays were implemented to investigate the transcriptional responses of Chromohalobacter salexigens to osmotic and heat stress. These conditions trigger the synthesis of ectoine and hydroxyectoine, two compatible solutes of biotechnological interest. Our findings revealed that both stresses make a significant impact on C. salexigens global physiology. Apart from compatible solute metabolism, the most relevant adaptation mechanisms were related to “oxidative- and protein-folding- stress responses”, “modulation of respiratory chain and related components”, and “ion homeostasis”. A general salt-dependent induction of genes related to the metabolism of ectoines, as well as repression of ectoine degradation genes by temperature, was observed. Different oxidative stress response mechanisms, secondary or primary, were induced at low and high salinity respectively, and repressed by temperature. A higher sensitivity to H2O2 was observed at high salinity, regardless of temperature. Low salinity induced genes involved in “protein-folding-stress response”, suggesting disturbance of protein homeostasis. Transcriptional shift of genes encoding three types of respiratory NADH dehydrogenases, ATP synthase, quinone pool, Na+/H+ antiporters, and sodium-solute symporters, was observed depending on salinity and temperature, suggesting modulation of the components of the respiratory chain and additional systems involved in the generation of H+ and/or Na+ gradients. Remarkably, the Na+ intracellular content remained constant regardless of salinity and temperature. Disturbance of Na+- and H+-gradients with specific ionophores suggested that both gradients influence ectoine production, but with differences depending on the solute, salinity, and temperature conditions. Flagellum genes were strongly induced by salinity, and further induced by temperature. However, salt-induced cell motility was reduced at high temperature, possibly caused by an alteration of Na+ permeability by temperature, as dependence of motility on Na+-gradient was observed. The transcriptional induction of genes related to the synthesis and transport of siderophores correlated with a higher siderophore production and intracellular iron content only at low salinity. In addition, compared to low salinity external iron increased hydroxyectoine accumulation by 20% at high salinity, but reduced the intracellular content of ectoines by 50% at high salinity plus high temperature. These findings support the relevance of iron homeostasis for osmoadaptation, thermoadaptation and accumulation of ectoines, in C. salexigens

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The minimum low-salt stimulon in Vibrio parahaemolyticus

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