How to Make a Living by Exhaling Methane

Abstract

Methane produced in the biosphere is derived from two major pathways. Conversion of the methyl group of acetate to CH4 in the aceticlastic pathway accounts for at least two-thirds, and reduction of CO2 with electrons derived from H2, formate, or CO accounts for approximately one-third. Although both pathways have terminal steps in common, they diverge considerably in the initial steps and energy conservation mechanisms. Steps and enzymes unique to the CO2 reduction pathway are confined to methanogens and the domain Archaea. On the other hand, steps and enzymes unique to the aceticlastic pathway are widely distributed in the domain Bacteria, the understanding of which has contributed to a broader understanding of prokaryotic biology.