Newly Discovered Methane-Consuming Bacterium Could Help Reduce GHG Emissions from Landfills and Powerstations

23 November 2007

An international team of researchers has discovered a methane-consuming microorganism that lives in extremely acidic conditions. The bacterium could one day be used to reduce methane gas emissions from landfills. It could also help to cut methane emissions from geothermal power stations.

Aerobic methanotrophic bacteria (methanotrophs) consume methane diffusing away from methane-producing zones of soil and sediment. Some environments with active methane cycles—such as marshes and peat bogs—are very acidic; however, no cultured methanotroph grows optimally below pH 5. By contrast, the new bacterium is extremely acidophilic, and grows optimally at pH 2.0-2.5.

Unlike known methanotrophs, which belong to the phylum Proteobacteria, the new bacterium belongs to Verrucomicrobia. A paper on the new organism is published in the journal Nature.

Analysis of its draft genome detected genes encoding particulate methane monooxygenase that were homologous to genes found in methanotrophic proteobacteria. However, known genetic modules for methanol and formaldehyde oxidation were incomplete or missing, suggesting that the bacterium uses some novel methylotrophic pathways. Phylogenetic analysis of its three pmoA genes (encoding a subunit of particulate methane monooxygenase) placed them into a distinct cluster from proteobacterial homologues. This indicates an ancient divergence of Verrucomicrobia and Proteobacteria methanotrophs rather than a recent horizontal gene transfer of methanotrophic ability. The findings show that methanotrophy in the Bacteria is more taxonomically, ecologically and genetically diverse than previously thought, and that previous studies have failed to assess the full diversity of methanotrophs in acidic environments.

Globally, acidic environments generate significant quantities of methane. Scientists had suspected that a proportion of the methane generated by these sources was being consumed by bacteria living in the environments.

Our discovery has demonstrated that methane-consuming organisms do live in highly acidic environments. Without them, the amount of methane entering the atmosphere would be much greater. Ultimately, it may be possible to implant this organism, or a similar one, in landfills and cut methane emissions into the atmosphere.

—Matthew Stott, GNS Science

The researchers found the microorganism living in the Hell’s Gate geothermal areas in Rotorua, New Zealand. GNS Science microbiologist Peter Dunfield, who isolated the bacterium, has tentatively named it Methylokorus infernorum, which is a latinized description of its methane food source, the ‘hellish’ location of its discovery, and also a description of a structure within its cell that resembles a Koru.

GNS Science worked with colleagues at the University of Hawaii to sequence the genome of the bacterium.

The discovery stems from a collaboration between GNS Science and the owner and operator of Hell’s Gate, Tikitere Trust. The agreement between the two organizations includes the sharing of any benefits that might accrue from scientific discoveries.

Resources

• Peter F. Dunfield et. al., “Methane oxidation by an extremely acidophilic bacterium of the phylum Verrucomicrobia” Nature advance online publication 14 November 2007 | doi:10.1038/nature06411