Department of Civil and Environmental Engineering, Stanford University, Stanford, CA, USA.
Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.
Environ Microbiol. 2020 Aug;22(8):3188-3204. doi: 10.1111/1462-2920.15061. Epub 2020 Jun 4.
Uncultured members of the Chloroflexi phylum are highly enriched in numerous subseafloor environments. Their metabolic potential was evaluated by reconstructing 31 Chloroflexi genomes from six different subseafloor habitats. The near ubiquitous presence of enzymes of the Wood-Ljungdahl pathway, electron bifurcation, and ferredoxin-dependent transport-coupled phosphorylation indicated anaerobic acetogenesis was central to their catabolism. Most of the genomes simultaneously contained multiple degradation pathways for complex carbohydrates, detrital protein, aromatic compounds, and hydrogen, indicating the coupling of oxidation of chemically diverse organic substrates to ubiquitous CO reduction. Such pathway combinations may confer a fitness advantage in subseafloor environments by enabling these Chloroflexi to act as primary fermenters and acetogens in one microorganism without the need for syntrophic H consumption. While evidence for catabolic oxygen respiration was limited to two phylogenetic clusters, the presence of genes encoding putative reductive dehalogenases throughout the phylum expanded the phylogenetic boundary for potential organohalide respiration past the Dehalococcoidia class.
未经培养的绿弯菌门成员在众多海底环境中高度富集。通过从六个不同海底栖息地重建 31 个绿弯菌基因组，评估了它们的代谢潜力。木-林克达尔途径、电子分叉和依赖铁氧还蛋白的运输偶联磷酸化的酶几乎普遍存在，表明厌氧乙酰生成是它们分解代谢的核心。大多数基因组同时包含多种用于复杂碳水化合物、碎屑蛋白、芳香族化合物和氢的降解途径，表明化学多样的有机底物的氧化与普遍的 CO 还原相偶联。这种途径组合可能通过使这些绿弯菌在无需共生 H 消耗的情况下在一个微生物中充当主要发酵菌和乙酰生成菌，从而在海底环境中赋予适应性优势。虽然证据表明存在分解代谢的需氧呼吸仅限于两个系统发育群，但整个门中存在编码潜在的还原脱卤酶的基因，将潜在的有机卤化物呼吸的系统发育边界扩展到了 Dehalococcoidia 类之外。
