Methanogenesis facilitated by geobiochemical iron cycle in a novel syntrophic methanogenic microbial community.

Production and emission of methane have been increasing concerns due to its significant effect on global climate change and the carbon cycle. Here we report facilitated methane production from acetate by a novel community of methanogens and acetate oxidizing bacteria in the presence of poorly crystalline akaganeite slurry. Comparative analyses showed that methanogenesis was significantly enhanced by added akaganeite and acetate was mostly stoichiometrically converted to methane. Electrons produced from anaerobic acetate oxidation are transferred to akaganeite nanorods that likely prompt the transformation into goethite nanofibers through a series of biogeochemical processes of soluble Fe(II) readsorption and Fe(III) reprecipitation. The methanogenic archaea likely harness the biotransformation of akaganeite to goethite by the Fe(III)-Fe(II) cycle to facilitate production of methane. These results provide new insights into biogeochemistry of iron minerals and methanogenesis in the environment, as well as the development of sustainable methods for microbial methane production.