Isoprene production by Sphagnum moss is balanced by microbial uptake, as revealed by selective inhibitors

Northern peatlands, ecosystems which store enormous amounts of carbon, and yet are major sources of methane and plant-derived volatiles including isoprene, are predicted to be greatly affected by climate change. Isoprene, the major volatile secondary metabolite released by plants, can support the carbon and energy needs of a variety of bacteria. Here we show that Sphagnum moss from an acidic bog harboured highly active isoprene degraders which consumed the vast majority of the plant-produced isoprene, preventing its release to the atmosphere. We quantified the potential for microbial isoprene uptake in the moss and, using alkyne inhibitors specific to either isoprene monooxygenase of bona fide isoprene degraders, or to the enzymes of other microbes capable of its fortuitous co-oxidation, we show that methane utilizers, for example, did not oxidise significant isoprene in incubations. Our technique enabled the separate quantification of plant isoprene production and microbial uptake, revealing that although atmospheric isoprene concentrations are typically low, the microbes contained in, or in close association with the moss were capable of isoprene uptake at the plant-generated isoprene concentration. Analysis of the bacterial community suggested that the isoprene degraders in this environment belonged to novel groups distinct from extant strains with this capability.