Abstract
Methanogenic archaea are a group of microorganisms found in the gastrointestinal tract of various herbivores and humans; however, the quantity (intensity) of methane emissions during feed digestion varies. Macropodids, such as the Eastern Gray Kangaroo (Macropus giganteus), are considered to be low methane-emitting animals, but their gut methanogenic archaea remain poorly characterized. Characterizing methanogens from animals with low methane emissions offers the potential to develop strategies and interventions that reduce methane emissions from livestock. In this study, we describe a novel strain of Methanobrevibacter gottschalkii (EGK), the first Methanobrevibacter isolate from a marsupial host. Comparative analyses with other M. gottschalkii genomes revealed a high degree of gene conservation, along with strain-specific differences in genes related to membrane transport, xenobiotic metabolism, nucleotide metabolism, and the metabolism of cofactors and vitamins. Notably, the M. gottschalkii EGK genome contains multiple copies of large proviral elements, likely acquired through integration events in this strain. M. gottschalkii EGK is the first isolated representative of Methanobrevibacter from a low methane-emitting animal, providing a valuable reference genome to identify metabolic targets for methane mitigation.