Mixing it up – methanotrophs use hydrogen as alternative energy source

Chris Greening, from the Centre for Geometric Biology, has been working with collaborators from GNS Science, University of Otago, Scion, and Montana State University, to provide evidence that aerobic methane-oxidising bacteria (methantrophs) are able to meet energy and biomass demands in variable environments, by using hydrogen as an alternative energy source.

Methanotrophs thrive in areas where methane (CH4) fluxes are high such as peat bogs, wetlands, rice paddies and geothermal habitats and have been considered specialist users of single carbon compounds such as methane.  But, these types of bacteria also exist within soil and marine systems where CH4 and oxygen (O2) concentrations fluctuate more widely.

This led Chris and colleagues to hypothesise that methanotrophs must be able to supplement metabolism of CH4 and O2 with other energy yielding strategies to support growth.

The research team conducted an interdisciplinary study to investigate the role of hydrogen (H2) as an important electron donor allowing organisms to meet carbon and energy demands in response to fluctuating CH4 and O2 availability.

Field studies demonstrated that bacteria in the phylum Verrumicrobia simultaneously oxidised CH4 and H2 in geothermally heated soils. What is more, laboratory studies confirmed that a representative of the Verrumicrobia depended on H2 consumption when CH4 and O2 were experimentally varied.

Members of the research team taking soil samples from geothermal habitat in New Zealand.

This evidence, coupled with genome surveys, led the researchers to conclude that H2 oxidation expands the ecological niche of methanotrophs, enabling them to meet energy and biomass demands in dynamic environments where O2 and CH4 concentrations are variable.

This finding has broad implications for future investigations into the ecology of methanotrophs – primary players in greenhouse-gas mitigation.

This research is published in The International Society for Microbial Ecology (ISME) Journal