Anaerobic methane oxidation linked to Fe(III) reduction in a Candidatus Methanoperedens-enriched consortium from the cold Zoige wetland at Tibetan Plateau

Anaerobic oxidation of methane (AOM) is a microbial process degrading ample methane in anoxic environments, and Ca. Methanoperedens mediated nitrate- or metal-reduction linked AOM is believed important in freshwater systems. This work, via 16S rRNA gene diversity survey and 16S rRNA quantification, found abundant Ca. Methanoperedens along with iron in the cold Zoige wetland at Tibetan Plateau. The wetland soil microcosm performed Fe(III) reduction, rather than nitrate- nor sulphate-reduction, coupled methane oxidation (3.87 mu mol d(-1)) with 32.33 mu mol Fe(II) accumulation per day at 18 degrees C, but not at 30 degrees C. A metagenome-assembled genome (MAG) recovered from the microcosm exhibits similar to 74% average nucleotide identity with the reported Ca. Methanoperedens spp. that perform Fe(III) reduction linked AOM, thus a novel species Ca. Methanoperedens psychrophilus was proposed. Ca. M. psychrophilus contains the whole suite of CO2 reductive methanogenic genes presumably involving in AOM via a reverse direction, and comparative genome analysis revealed its unique gene categories: the multi-heme clusters (MHCs) cytochromes, the S-layer proteins highly homologous to those recovered from lower temperature environments and type IV pili, those could confer Ca. M. psychrophilus of cold adaptability. Therefore, this work reports the first methanotroph implementing AOM in an alpine wetland.

Automated summary

This study identified abundant Ca. Methanoperedens and iron in the cold Zoige wetland at Tibetan Plateau, proposing a novel species, Ca. Methanoperedens psychrophilus, which contains a full suite of CO2 reductive methanogenic genes and unique gene categories related to cold adaptability. This work reports the first evidence of a methanotroph performing anaerobic oxidation of methane in an alpine wetland.