Zetaproteobacteria are obligate chemolithoautotrophs that oxidize Fe(II) as an electron and energy source, and play significant roles in nutrient cycling and primary production in the marine biosphere. Zetaproteobacteria thrive under microoxic conditions near oxic-anoxic interfaces, where they catalyze Fe(II) oxidation faster than the abiotic reaction with oxygen. Neutrophilic Fe(II) oxidizing bacteria produce copious amounts of insoluble iron oxyhydroxides as a by-product of their metabolism. Oxygen consumption by aerobic respiration and formation of iron oxyhydroxides at oxic-anoxic interfaces can result in periods of oxygen limitation for bacterial cells. Under laboratory conditions, all Zetaproteobacteria isolates have been shown to strictly require oxygen as an electron acceptor for growth, and anaerobic metabolism has not been observed. However, genomic analyses indicate a range of potential anaerobic pathways present in Zetaproteobacteria. Heterologous expression of proteins from Mariprofundus ferrooxydans PV-1, including pyruvate formate lyase and acetate kinase, further support a capacity for anaerobic metabolism. Here we define auxiliary anaerobic metabolism as a mechanism to provide maintenance energy to cells and suggest that it provides a survival advantage to Zetaproteobacteria in environments with fluctuating oxygen availability.

中文翻译：

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专心有氧的Zetaproteobacteria中辅助厌氧代谢的证据。

Zetaproteobacteria是专性化能自养生物，能氧化Fe（II）作为电子和能源，并在海洋生物圈的养分循环和初级生产中发挥重要作用。Zetaproteobacteria细菌在含氧-缺氧界面附近的微含氧条件下壮成长，在那里它们催化Fe（II）氧化的速度比与氧的非生物反应更快。中性Fe（II）氧化细菌会产生大量不溶的羟基氧化铁，作为其代谢的副产品。有氧呼吸耗氧和在氧-缺氧界面形成羟基氧化铁会导致细菌细胞缺氧。在实验室条件下，已显示所有分离的细菌都需要氧作为生长的电子受体，并且尚未观察到厌氧代谢。但是，基因组分析表明，Zetaproteobacteria中存在一系列潜在的厌氧途径。来自马氏螺旋藻PV-1的蛋白质的异源表达，包括丙酮酸甲酸裂解酶和乙酸激酶，进一步支持了厌氧代谢的能力。在这里，我们将辅助厌氧代谢定义为一种向细胞提供维持能量的机制，并建议其在氧利用率波动的环境中为Zetaproteobacteria提供生存优势。