Bark-dwelling methanotrophic bacteria decrease methane emissions from trees

Tree stems are an important and unconstrained source of methane, yet it is uncertain whether internal controls within tree bark (i.e. microbial methanotrophy) may reduce methane emissions. Here, we demonstrate that unique microbial communities dominated by methane oxidising bacteria (MOB) dwell within bark of Melaleuca quinquenervia; a common, invasive and globally distributed lowland species. Laboratory incubations of methane inoculated bark showed distinct methane uptake and isotopic δ13C-CH4 enrichment characteristic of MOB. Molecular analysis discovered unique microbial communities reside within bark, with MOB comprising up to 25 % of the total community, primarily from the Methylomonas genus. Methanotroph abundance was positively correlated to methane uptake rates. Field-based methanotroph inhibition experiments demonstrate that bark-dwelling MOB reduce methane emissions by ~36 %. These multiple, complementary lines of evidence indicate that bark-dwelling MOB represent a novel and potentially significant methane sink, and an important research frontier.