Further expansion of methane metabolism in the Archaea

Abstract

The recent discovery of key methane-metabolizing genes in the genomes from the archaeal phyla Bathyarchaeota and Verstraetearchaeota has expanded our understanding of the distribution of methane metabolism outside of the phylum Euryarchaeota. Here, we recovered two near-complete crenarchaeotal metagenome-assembled genomes (MAGs) from circumneutral hot springs that contain genes for methanogenesis, including the genes that encode for the key methyl-coenzyme M reductase (MCR) complex. These newly recovered archaea phylogenetically cluster with Geoarchaeota (deep lineage of archaeal order Thermoproteales), and the MCR-encoding genes clustered with the recently reported methanogens within the Verstraetearchaeota. In addition, genes encoding hydroxybutyryl-CoA dehydratase were identified in the newly recovered methanogens, indicating they might carry out the {beta}-oxidation process. Together, our findings further expanded the methane metabolism outside the phylum Euryarchaeota.