Clostridia are obligate anaerobic bacteria that can produce solvents such as acetone, butanol and ethanol. Alcohol dehydrogenases (ADHs) play a key role in solvent production; however, their regulatory mechanisms remain largely unknown. In this study, we characterized the regulatory mechanisms of two ADH‐encoding genes in C. beijerinckii. SigL (sigma factor σ⁵⁴) was found to be required for transcription of adhA1 and adhA2 genes. Moreover, a novel transcriptional activator AdhR was identified, which binds to the σ⁵⁴ promoter and activates σ⁵⁴‐dependent transcription of adhA1 and adhA2. Clostridia beijerinckii mutants deficient in SigL or AdhR showed severely impaired butanol and ethanol production as well as altered acetone and butyrate synthesis. Overexpression of SigL resulted in significantly improved solvent production by C. beijerinckii when butyrate was added to cultures. Our results reveal SigL as a novel engineering target for improving solvent production by C. beijerinckii and other solvent‐producing clostridia. Moreover, this study gains an insight into regulation of alcohol metabolism in diverse clostridia.

中文翻译：

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通过 sigma-54 因子和转录激活因子 AdhR 在拜氏梭菌中控制溶剂的产生。

梭状芽胞杆菌是专性厌氧菌，可产生丙酮、丁醇和乙醇等溶剂。酒精脱氢酶 (ADH) 在溶剂生产中发挥着关键作用；然而，它们的调节机制在很大程度上仍然未知。在这项研究中，我们描述了C. beijerinckii中两个 ADH 编码基因的调控机制。发现 SigL（sigma 因子 σ ⁵⁴）是adhA1和adhA2基因转录所必需的。此外，还鉴定了一种新的转录激活因子 AdhR，它与 σ ⁵⁴启动子结合并激活adhA1和adhA2的 σ ⁵⁴依赖性转录。拜氏梭菌缺乏 SigL 或 AdhR 的突变体表现出严重受损的丁醇和乙醇生产以及改变的丙酮和丁酸盐合成。当将丁酸盐添加到培养物中时，SigL 的过表达导致拜氏梭菌的溶剂产量显着提高。我们的结果表明，SigL 是一种新的工程目标，可用于改善拜氏梭菌和其他产溶剂梭状芽胞杆菌的溶剂生产。此外，这项研究深入了解了不同梭状芽胞杆菌中酒精代谢的调节。