Lever Mark A, Alperin Marc J, Hinrichs Kai-Uwe, Teske Andreas
Department of Marine Science, Marine Science Institute, University of Texas at Austin, Port Aransas, TX, United States.
Earth, Marine and Environmental Sciences, University of North Carolina at Chapel Hill, Chapel Hill, NC, United States.
Front Microbiol. 2023 May 12;14:1192029. doi: 10.3389/fmicb.2023.1192029. eCollection 2023.
The production and anaerobic oxidation of methane (AOM) by microorganisms is widespread in organic-rich deep subseafloor sediments. Yet, the organisms that carry out these processes remain largely unknown. Here we identify members of the methane-cycling microbial community in deep subsurface, hydrate-containing sediments of the Peru Trench by targeting functional genes of the alpha subunit of methyl coenzyme M reductase (). The profile reveals a distinct community zonation that partially matches the zonation of methane oxidizing and -producing activity inferred from sulfate and methane concentrations and carbon-isotopic compositions of methane and dissolved inorganic carbon (DIC). A appears absent from sulfate-rich sediments that are devoid of methane, but A sequences belonging to putatively methane-oxidizing ANME-1a-b occur from the zone of methane oxidation to several meters into the methanogenesis zone. A sister group of ANME-1a-b, referred to as ANME-1d, and members of putatively aceticlastic (formerly ) occur throughout the remaining methanogenesis zone. Analyses of 16S rRNA and A-mRNA indicate that the methane-cycling community is alive throughout (rRNA to 230 mbsf) and active in at least parts of the sediment column (mRNA at 44 mbsf). Carbon-isotopic depletions of methane relative to DIC (-80 to -86‰) suggest mostly methane production by CO reduction and thus seem at odds with the widespread detection of ANME-1 and . We explain this apparent contradiction based on recent insights into the metabolisms of both ANME-1 and , which indicate the potential for methanogenetic growth by CO reduction in both groups.
微生物产生甲烷及甲烷厌氧氧化（AOM）的现象在富含有机物的深海海底沉积物中广泛存在。然而，执行这些过程的生物体在很大程度上仍然未知。在这里，我们通过靶向甲基辅酶M还原酶α亚基的功能基因，鉴定了秘鲁海沟深层地下含天然气水合物沉积物中甲烷循环微生物群落的成员。该图谱揭示了一个独特的群落分区，该分区与根据硫酸盐和甲烷浓度以及甲烷和溶解无机碳（DIC）的碳同位素组成推断出的甲烷氧化和产生活动的分区部分匹配。在没有甲烷的富含硫酸盐的沉积物中似乎不存在A，但属于假定的甲烷氧化ANME-1a-b的A序列从甲烷氧化带一直到甲烷生成带的数米处都有出现。ANME-1a-b的一个姐妹群，称为ANME-1d，以及假定的乙酸裂解菌（以前称为）的成员出现在其余的甲烷生成带中。对16S rRNA和A-mRNA的分析表明，甲烷循环群落自始至终都是有生命的（rRNA到230米海底以下），并且至少在沉积物柱的某些部分是活跃的（44米海底以下有mRNA）。甲烷相对于DIC的碳同位素亏损（-80至-86‰）表明主要是通过CO还原产生甲烷，因此似乎与广泛检测到的ANME-1和相矛盾。我们基于对ANME-1和两者代谢的最新见解来解释这一明显的矛盾，这表明两组中都有通过CO还原进行产甲烷生长的潜力。
