Global prevalence of methane oxidation by symbiotic bacteria in peat-moss ecosystems

Peat bogs store up to a third of all terrestrial carbon on Earth(1), and are one of the largest natural sources of atmospheric methane(2). Anaerobic degradation of submerged Sphagnum species-mosses that are prevalent in peat bogs across the globe-produces significant quantities of methane in these systems. However, a study on peat mosses in the Netherlands revealed that a large fraction of this methane is consumed by aerobic methane-oxidizing bacteria, known as methanotrophs(3); in return, the methanotrophs provide Sphagnum mosses with carbon(3). Here, we show that Sphagnum-associated methane oxidation occurs ubiquitously across the globe. We collected Sphagnum mosses from pools, lawns and hummocks in nine Sphagnum-dominated peatlands across the world, and measured their capacity to oxidize methane in a series of laboratory incubations. All mosses were capable of oxidizing methane. The rate of methane oxidation increased with temperature, and was most pronounced in submerged mosses, collected from peatland pools. According to DNA microarray analyses, the methanotrophic community responsible for methane oxidation was highly diverse. C-13 labelling revealed that methane-derived carbon was incorporated into plant lipids when mosses were submerged, indicative of a mutually beneficial symbiosis between mosses and methanotrophs. Our findings suggest that the interaction between methanotrophs and Sphagnum mosses may play a role in carbon recycling in waterlogged Sphagnum vegetation, potentially reducing methane emissions.