Department of Land Resources and Environmental Sciences, Montana State University, Bozeman, MT, USA.
Center for Biofilm Engineering, Montana State University, Bozeman, MT, USA.
Nat Microbiol. 2019 Apr;4(4):614-622. doi: 10.1038/s41564-019-0362-4. Epub 2019 Mar 4.
Phylogenetic and geological evidence supports the hypothesis that life on Earth originated in thermal environments and conserved energy through methanogenesis or sulfur reduction. Here we describe two populations of the deeply rooted archaeal phylum Korarchaeota, which were retrieved from the metagenome of a circumneutral, suboxic hot spring that contains high levels of sulfate, sulfide, methane, hydrogen and carbon dioxide. One population is closely related to 'Candidatus Korarchaeum cryptofilum OPF8', while the more abundant korarchaeote, 'Candidatus Methanodesulfokores washburnensis', contains genes that are necessary for anaerobic methane and dissimilatory sulfur metabolisms. Phylogenetic and ancestral reconstruction analyses suggest that methane metabolism originated in the Korarchaeota, whereas genes for dissimilatory sulfite reduction were horizontally transferred to the Korarchaeota from the Firmicutes. Interactions among enzymes involved in both metabolisms could facilitate exergonic, sulfite-dependent, anaerobic oxidation of methane to methanol; alternatively, 'Ca. M. washburnensis' could conduct methanogenesis and sulfur reduction independently. Metabolic reconstruction suggests that 'Ca. M. washburnensis' is a mixotroph, capable of amino acid uptake, assimilation of methane-derived carbon and/or CO fixation by archaeal type III-b RuBisCO for scavenging ribose carbon. Our findings link anaerobic methane metabolism and dissimilatory sulfur reduction within a single deeply rooted archaeal population and have implications for the evolution of these traits throughout the Archaea.
系统发生和地质证据支持这样的假说，即在地球上的生命起源于热环境，并通过产甲烷作用或硫还原来保存能量。在这里，我们描述了深根系古菌门 Korarchaeota 的两个种群，它们是从含有高浓度硫酸盐、硫化物、甲烷、氢气和二氧化碳的中性、亚缺氧温泉的宏基因组中回收的。一个种群与“疑似 Korarchaeum cryptofilum OPF8”密切相关，而更丰富的 korarchaeote“疑似 Methanodesulfokores washburnensis”则包含了厌氧甲烷和异化硫代谢所必需的基因。系统发生和祖先重建分析表明，甲烷代谢起源于 Korarchaeota，而异化亚硫酸盐还原基因则从 Firmicutes 水平转移到 Korarchaeota。两种代谢相关酶之间的相互作用可以促进硫酸盐依赖的、放能的、厌氧甲烷氧化为甲醇；或者，“Ca. M. washburnensis”可以独立地进行产甲烷作用和硫还原。代谢重建表明，“Ca. M. washburnensis”是一种混合营养体，能够通过古菌类型 III-b RuBisCO 摄取氨基酸、利用甲烷衍生的碳和/或 CO 固定来固定核糖碳。我们的发现将厌氧甲烷代谢和异化硫还原联系在一个单一的深根系古菌种群中，并对这些特征在整个古菌中的进化具有重要意义。
