Previously, methanogenic organisms had only been described in the Euryarchaeota. Now, Evans et al. report two near-complete genomes that provide strong evidence for methanogenesis in a second archaeal phylum, the Bathyarchaeota. The genomes — obtained from an Australian methane well — contain genes indicative of methylotrophic methanogenesis using a diverse set of methylated compounds. Interestingly, one of the genomes also contains genes for complex fermentation and the other also contains genes for β-oxidation; neither of these processes have previously been seen in methanogens. By contrast, structural prediction suggested that both genomes encode a functional methyl-coenzyme M reductase complex (MCR), a universal feature of methanogens. A survey of metagenomes from geographically disparate high-methane- flux environments identified additional non-euryarchaeotal examples of genes encoding MCR components. The authors propose that methanogenesis arose in a common ancestor of the two phyla, rather than in the Euryarchaeota, and thus has a more ancient origin than has sometimes been suggested.
References
Evans, P. N. et al. Methane metabolism in the archaeal phylum Bathyarchaeota revealed by genome-centric metagenomics. Science 350, 434–438 (2015)
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Attar, N. A new phylum for methanogens. Nat Rev Microbiol 13, 739 (2015). https://doi.org/10.1038/nrmicro3589
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DOI: https://doi.org/10.1038/nrmicro3589