Abstract
Anaerobic methane oxidation in archaea is often presented to operate via a pathway of "reverse methanogenesis". However, if the cumulative reactions of a methanogen are run in reverse there is no apparent way to conserve energy. Recent findings suggest that chemiosmotic coupling enzymes known from their use in methylotrophic and acetoclastic methanogens-in addition to unique terminal reductases-biochemically facilitate energy conservation during complete CH(4) oxidation to CO(2). The apparent enzyme modularity of these organisms highlights how microbes can arrange their energy metabolisms to accommodate diverse chemical potentials in various ecological niches, even in the extreme case of utilizing "reverse" thermodynamic potentials.