Chemoautotrophic bacteria from the SUP05 clade often dominate anoxic waters within marine oxygen minimum zones (OMZs) where they use energy gained from the oxidation of reduced sulfur to fuel carbon fixation. Some of these SUP05 bacteria are facultative aerobes that can use either nitrate or oxygen as a terminal electron acceptor making them ideally suited to thrive at the boundaries of OMZs where they experience fluctuations in dissolved oxygen (DO). SUP05 metabolism in these regions, and therefore the biogeochemical function of SUP05, depends largely on their sensitivity to oxygen. We evaluated growth and quantified differences in gene expression in Ca. T. autotrophicus strain EF1 from the SUP05 clade under high DO (22 μM), anoxic, and low DO (3.8 μM) concentrations. We show that strain EF1 cells respire oxygen and nitrate and that cells have higher growth rates, express more genes, and fix more carbon when oxygen becomes available for aerobic respiration. Evidence that facultatively aerobic SUP05 are more active and respire nitrate when oxygen becomes available at low concentrations suggests that they are an important source of nitrite across marine OMZ boundary layers.

中文翻译：

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SUP05 在低 DO 生长条件下的代谢灵活性

来自 SUP05 进化枝的化学自养细菌通常在海洋氧气最低区 (OMZ) 内的缺氧水域中占主导地位，在那里它们利用从还原硫氧化中获得的能量来为碳固定提供燃料。其中一些 SUP05 细菌是兼性需氧菌，可以使用硝酸盐或氧气作为末端电子受体，使其非常适合在 OMZ 的边界处繁衍，在那里它们会经历溶解氧 (DO) 的波动。这些区域的 SUP05 代谢以及因此 SUP05 的生物地球化学功能在很大程度上取决于它们对氧气的敏感性。我们评估了Ca中基因表达的生长和量化差异. 在高 DO (22 μM)、缺氧和低 DO (3.8 μM) 浓度下来自 SUP05 进化枝的 T. autotrophicus 菌株 EF1。我们表明 EF1 菌株会呼吸氧气和硝酸盐，并且当氧气可用于有氧呼吸时，细胞具有更高的生长速率、表达更多的基因并固定更多的碳。有证据表明，兼性好氧 SUP05 在低浓度氧气可用时更活跃并呼吸硝酸盐，这表明它们是海洋 OMZ 边界层中亚硝酸盐的重要来源。