Identification of Methyl Coenzyme M Reductase A ( mcrA ) Genes Associated with Methane-Oxidizing Archaea

作者：Steven Hallam, Peter R. Girguis, Christina M. Preston, Paul M. Richardson, Edward F. DeLong · 发表于：Applied and Environmental Microbiology · 年份：2003 · DOI：10.1128/aem.69.9.5483-5491.2003 · 被引用次数：393 · 研究领域：Methane Hydrates and Related Phenomena、Porphyrin Metabolism and Disorders、Microbial bioremediation and biosurfactants

Phylogenetic and stable-isotope analyses implicated two methanogen-like archaeal groups, ANME-1 and ANME-2, as key participants in the process of anaerobic methane oxidation. Although nothing is known about anaerobic methane oxidation at the molecular level, the evolutionary relationship between methane-oxidizing archaea (MOA) and methanogenic archaea raises the possibility that MOA have co-opted key elements of the methanogenic pathway, reversing many of its steps to oxidize methane anaerobically. In order to explore this hypothesis, the existence and genomic conservation of methyl coenzyme M reductase (MCR), the enzyme catalyzing the terminal step in methanogenesis, was studied in ANME-1 and ANME-2 archaea isolated from various marine environments. Clone libraries targeting a conserved region of the alpha subunit of MCR (mcrA) were generated and compared from environmental samples, laboratory-incubated microcosms, and fosmid libraries. Four out of five novel mcrA types identified from these sources were associated with ANME-1 or ANME-2 group members. Assignment of mcrA types to specific phylogenetic groups was based on environmental clone recoveries, selective enrichment of specific MOA and mcrA types in a microcosm, phylogenetic congruence between mcrA and small-subunit rRNA tree topologies, and genomic context derived from fosmid sequences. Analysis of the ANME-1 and ANME-2 mcrA sequences suggested the potential for catalytic activity based on conservation of active-site ...