Contribution of RpoS to metabolic efficiency and ectoines synthesis during the osmo- and heat-stress response in the halophilic bacterium Chromohalobacter salexigens.
Contribution of RpoS to metabolic efficiency and ectoines synthesis during the osmo- and heat-stress response in the halophilic bacterium Chromohalobacter salexigens.
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DOI：
10.1111/1758-2229.12249
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发表时间：
2015-04
影响因子：
3.3
通讯作者：
M. Salvador;M. Argandoña;J. Pastor;V. Bernal;M. Cánovas;L. Csonka;J. J. Nieto-J.;C. Vargas
中科院分区：
文献类型：
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作者：
M. Salvador;M. Argandoña;J. Pastor;V. Bernal;M. Cánovas;L. Csonka;J. J. Nieto-J.;C. Vargas
嗜盐菌是一种嗜盐γ-变形菌，其通过分别积累四氢嘧啶和羟基四氢嘧啶来响应渗透胁迫和热胁迫。进化已经优化了它的代谢，以支持高产量的四氢嘧啶。我们分析了C. salexigens代谢和四氢嘧啶合成。在长期适应的细胞中，rpoS菌株对温度敏感，但对温度不敏感，并且显示出不变的四氢嘧啶含量，表明RpoS调节四氢嘧啶（s）-非依赖性的温度适应机制。RpoS参与了C. salexigens代谢适应压力，葡萄糖氧化的早期步骤，通过恩特纳-杜道夫途径在rpoS突变体失调，导致改善的代谢效率在低盐度。此外，在低盐下，rpoS菌株显示丙酮酸（但不是乙酸）溢流减少，这可能与葡萄糖酸盐产生和/或随后代谢的减缓有关。有趣的是，RpoS似乎并不是触发四氢嘧啶合成对渗透压或温度升高的即时转录反应的主要调节因子。然而，它有助于表达的ect基因在细胞先前适应低或高盐度。
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.