Microbial populations can maximize fitness in dynamic environments through bet hedging, a process wherein a subpopulation assumes a phenotype not optimally adapted to the present environment but well adapted to an environment likely to be encountered. Here, we show that oxygen induces fluctuating expression of the trimethylamine oxide (TMAO) respiratory system of Escherichia coli, diversifying the cell population and enabling a bet-hedging strategy that permits growth following oxygen loss. This regulation by oxygen affects the variance in gene expression but leaves the mean unchanged. We show that the oxygen-sensitive transcription factor IscR is the key regulator of variability. Oxygen causes IscR to repress expression of a TMAO-responsive signaling system, allowing stochastic effects to have a strong effect on the output of the system and resulting in heterogeneous expression of the TMAO reduction machinery. This work reveals a mechanism through which cells regulate molecular noise to enhance fitness.

中文翻译：

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细菌信号网络中调节的随机性允许耐受快速的环境变化。

微生物种群可以通过对冲来最大程度地适应动态环境，在此过程中，亚群采用的表型并非最适合当前环境，而是非常适合可能遇到的环境。在这里，我们表明氧气诱导大肠杆菌三甲胺氧化物（TMAO）呼吸系统的波动表达，使细胞群体多样化，并实现了一种对冲策略，该策略允许氧气流失后的增长。氧气的这种调节影响基因表达的差异，但均值保持不变。我们表明，氧敏感的转录因子IscR是变异性的关键调节因子。氧气导致IscR抑制TMAO响应信号系统的表达，允许随机效应对系统的输出产生强烈影响，并导致TMAO还原机制的异构表达。这项工作揭示了一种机制，细胞可以通过这种机制调节分子噪音，从而增强适应性。