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Contribution of RpoS to metabolic efficiency and ectoines synthesis during the osmo‐ and heat‐stress response in the halophilic bacterium C hromohalobacter salexigens
Author(s) -
Salvador Manuel,
Argandoña Montserrat,
Pastor Jose M.,
Bernal Vicente,
Cánovas Manuel,
Csonka Laszlo N.,
Nieto Joaquín J.,
Vargas Carmen
Publication year - 2015
Publication title -
environmental microbiology reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.229
H-Index - 69
ISSN - 1758-2229
DOI - 10.1111/1758-2229.12249
Subject(s) - rpos , halophile , ectoine , biology , biochemistry , mutant , osmotic concentration , strain (injury) , metabolism , osmoprotectant , bacteria , chemistry , gene , gene expression , amino acid , genetics , promoter , anatomy , proline
Summary C hromohalobacter 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 E ntner– D oudoroff 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.