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.

中文翻译：

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在 Komagataeibacter medellinensis 中参与 FNR 样氧传感器在缺氧条件下的生存。

在乙酸发酵过程中，乙酸菌面临着由乙醇剧烈氧化成乙酸引起的耗氧压力。然而，对氧耗竭应激反应的分子机制仍然很大程度上未知。在这里，我们专注于 Komagataeibacter medellinensis 中的氧感应 FNR 同源物 FnrG。野生型和 fnrG 破坏菌株之间的比较转录组分析显示，FnrG 上调了 8 个基因（倍数变化> 3）。仅当 FnrG 厌氧重组时，重组 FnrG 才与特定的 DNA 序列结合。一个由乙酸激酶和木酮糖-5-磷酸/果糖-6-磷酸磷酸酮酶基因组成的操纵子被发现是在限氧条件下参与细胞存活的FnrG调节子。而且，过度表达这两个基因的菌株比含有空载体的野生型菌株积累了更多的乙酸。因此，这两个基因可能成为高产乙酸乙酸菌分子育种的新靶点。