title: Contribution of RpoS to metabolic efficiency and ectoines synthesis during the osmo- and heat-stress response in the halophilic bacterium Chromohalobacter salexigens.
abstract: Chromohalobacter salexigens is a halophilic γ-proteobacterium that responds to osmotic and heat stresses by accumulating ectoine and hydroxyectoine respectively. Evolution has optimized its metabolism to support high production of ectoines. We analysed the effect of an rpoS mutation in C. salexigens metabolism and ectoines synthesis. In long-term adapted cells, the rpoS strain was osmosensitive but not thermosensitive and showed unaltered ectoines content, suggesting that RpoS regulates ectoine(s)-independent osmoadaptive mechanisms. RpoS is involved in the regulation of C. salexigens metabolic adaptation to stress, as early steps of glucose oxidation through the Entner-Doudoroff pathway were deregulated in the rpoS mutant, leading to improved metabolic efficiency at low salinity. Moreover, a reduced pyruvate (but not acetate) overflow was displayed by the rpoS strain at low salt, probably linked to a slowdown in gluconate production and/or subsequent metabolism. Interestingly, RpoS does not seem to be the main regulator triggering the immediate transcriptional response of ectoine synthesis to osmotic or thermal upshifts. However, it contributed to the expression of the ect genes in cells previously adapted to low or high salinity.
authors.affiliation: Department of Microbiology and Parasitology, Faculty of Pharmacy, University of Seville, Seville, 41012, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Salvador
authors.forename: Montserrat
authors.initials: M
authors.lastname: Argandoña
authors.forename: Jose M
authors.initials: JM
authors.lastname: Pastor
authors.forename: Vicente
authors.initials: V
authors.lastname: Bernal
authors.forename: Manuel
authors.initials: M
authors.lastname: Cánovas
authors.forename: Laszlo N
authors.initials: LN
authors.lastname: Csonka
authors.forename: Joaquín J
authors.initials: JJ
authors.lastname: Nieto
authors.forename: Carmen
authors.initials: C
authors.lastname: Vargas
mesh_terms: D000599:Amino Acids, Diamino / Q000096:biosynthesis*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D055353:Chromohalobacter / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D015964:Gene Expression Regulation, Bacterial; D055786:Gene Knockout Techniques; D018869:Heat-Shock Response; D009997:Osmotic Pressure; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*
chemical_list: D000599:Amino Acids, Diamino; D001426:Bacterial Proteins; D012808:Sigma Factor; C121557:hydroxyectoine; C069567:sigma factor KatF protein, Bacteria; C045628:ectoine