Methane-oxidizing bacteria (methanotrophs) often coexist with methylotrophs that utilize methanol excreted by methanotrophs. Recently, we found that a facultative methylotroph, Methyloceanibacter caenitepidi Gela4T, possibly utilizes acetate rather than methanol in the coculture with a methanotroph, Methylocaldum marinum S8. Here, we examined the effects of oxygen concentrations on growth of and acetate excretion by M. marinum S8 in pure culture and the coculture with M. caenitepidi Gela4T. M. marinum S8 excreted acetate during the exponential growth phase not only under microaerobic (O2 concentrations of 3.5%-6%) but also under aerobic (O2 concentrations of 20%-31%) conditions. RNA-Seq analyses of M. marinum S8 cells grown under aerobic conditions suggested that phosphoketolase and acetate kinase were candidate genes involved in acetate production. Nonmethylotrophic bacteria, Cupriavidus necator NBRC 102504, could grow when cocultured with M. marinum S8, also supporting the existence of methanol-independent cross-feeding from M. marinum S8 under aerobic conditions.

中文翻译：

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甲烷氧化菌 Methylocaldum marinum S8 在需氧条件下的乙酸排泄。


甲烷氧化细菌（甲烷氧化菌）通常与利用甲烷氧化菌分泌的甲醇的甲基营养菌共存。最近，我们发现兼性甲基营养菌 Mmethyloceanibacter caenitepidi Gela4T 在与甲烷氧化菌 Methylocaldum marinum S8 共培养时可能利用乙酸盐而不是甲醇。在这里，我们研究了纯培养物以及与 M. caenitepidi Gela4T 共培养物中氧气浓度对 M. marinum S8 的生长和乙酸盐排泄的影响。 M. marinum S8在指数生长期不仅在微需氧（O2浓度3.5%-6%）条件下而且在好氧（O2浓度20%-31%）条件下分泌乙酸盐。对有氧条件下生长的 M. marinum S8 细胞的 RNA-Seq 分析表明，磷酸酮醇酶和乙酸激酶是参与乙酸生产的候选基因。非甲基营养菌 Cupriavidus necator NBRC 102504 与 M. marinum S8 共培养时可以生长，这也支持了在需氧条件下 M. marinum S8 存在不依赖甲醇的交叉喂养。