PT - JOURNAL ARTICLE AU - Carlo R. Carere AU - Kiel Hards AU - Karen M. Houghton AU - Jean F. Power AU - Ben McDonald AU - Christophe Collet AU - Daniel J. Gapes AU - Richard Sparling AU - Gregory M. Cook AU - Chris Greening AU - Matthew B. Stott TI - Aerobic H<sub>2</sub> respiration enhances metabolic flexibility of methanotrophic bacteria AID - 10.1101/075549 DP - 2016 Jan 01 TA - bioRxiv PG - 075549 4099 - http://biorxiv.org/content/early/2016/09/16/075549.short 4100 - http://biorxiv.org/content/early/2016/09/16/075549.full AB - Methanotrophic bacteria are important soil biofilters for the climate-active gas methane. The prevailing opinion is that these bacteria exclusively metabolise single-carbon, and in limited instances, short-chain hydrocarbons for growth. This specialist lifestyle juxtaposes metabolic flexibility, a key strategy for environmental adaptation of microorganisms. Here we show that a methanotrophic bacterium from the phylum Verrucomicrobia oxidises hydrogen gas (H2) during growth and persistence. Methylacidiphilum sp. RTK17.1 expresses a membrane-bound hydrogenase to aerobically respire molecular H2 at environmentally significant concentrations. While H2 oxidation did not support growth as the sole electron source, it significantly enhanced mixotrophic growth yields under both oxygen-replete and oxygen-limiting conditions and was sustained in non-growing cultures starved for methane. We propose that H2 is consumed by this bacterium for mixotrophic growth and persistence in a manner similar to other non-methanotrophic soil microorganisms. We have identified genes encoding oxygen-tolerant uptake hydrogenases in all publicly-available methanotroph genomes, suggesting that H2 oxidation serves a general strategy for methanotrophs to remain energised in chemically-limited environments.