Identification of methyl coenzyme M reductase A(mcrA) genes associated with methane-oxidizing archaea
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 orANME-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 amino acids. These results provide a basis for identifying methanotrophic archaea with mcrA sequences and define a functional genomic link between methanogenic and methanotrophic archaea.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Director. Office of Science. Biological and Environmental Research Program, Lawrence Livermore National Laboratory contract W-7405-ENG-48, Los Alamos National Laboratory contract W-7405-ENG-36; David and Lucille Packard Foundation (US)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 823087
- Report Number(s):
- LBNL-53923; AEMIDF; R&D Project: LWPFLS; TRN: US200415%%165
- Journal Information:
- Applied and Environmental Microbiology, Vol. 69, Issue 9; Other Information: Journal Publication Date: September 2003; PBD: 1 Sep 2003; ISSN 0099-2240
- Country of Publication:
- United States
- Language:
- English
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