Department of Biotechnology, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
Central Research Institute, Mizkan Holdings Co., Ltd., Handa, Aichi, Japan.
Biosci Biotechnol Biochem. 2021 Aug 25;85(9):2065-2075. doi: 10.1093/bbb/zbab121.
During acetic acid fermentation, acetic acid bacteria face oxygen depletion stress caused by the vigorous oxidation of ethanol to acetic acid. However, the molecular mechanisms underlying the response to oxygen depletion stress remain largely unknown. Here, we focused on an oxygen-sensing FNR homolog, FnrG, in Komagataeibacter medellinensis. Comparative transcriptomic analysis between the wild-type and fnrG-disrupted strains revealed that FnrG upregulated 8 genes (fold change >3). Recombinant FnrG bound to a specific DNA sequence only when FnrG was reconstituted anaerobically. An operon consisting of acetate kinase and xylulose-5-phosphate/fructose-6-phosphate phosphoketolase genes was found to be an FnrG regulon involved in cell survival under oxygen-limiting conditions. Moreover, a strain that overexpressed these 2 genes accumulated more acetic acid than the wild-type strain harboring an empty vector. Thus, these 2 genes could be new targets for the molecular breeding of acetic acid bacteria with high acetic acid productivity.
在乙酸发酵过程中，乙酸细菌会面临乙醇被剧烈氧化为乙酸所导致的缺氧胁迫。然而，对于应对缺氧胁迫的分子机制还知之甚少。在这里，我们专注于研究麦氏康宁酸醋杆菌中的一个氧感应 FNR 同源物 FnrG。野生型和 fnrG 敲除菌株之间的比较转录组分析表明，FnrG 上调了 8 个基因（倍数变化 >3）。只有在厌氧条件下重建 FnrG 时，FnrG 才能与特定的 DNA 序列结合。发现由乙酰激酶和木酮糖-5-磷酸/果糖-6-磷酸磷酸酮醇酶基因组成的操纵子是 FnrG 调控子，可参与在缺氧条件下的细胞存活。此外，过表达这 2 个基因的菌株比携带空载体的野生型菌株积累了更多的乙酸。因此，这 2 个基因可能成为具有高乙酸生产力的乙酸细菌分子育种的新目标。
