Communal metabolism of methane and the rare Earth element switch.

Metabolism of methane is an important part of biogeochemical cycling of carbon. Methane is also a major contributor to climate change. A specialized group of microbes that consume methane, the methanotrophs, represent a natural filter preventing an even faster accumulation of methane in the atmosphere. Methanotrophy can proceed via both anaerobic and aerobic modes. The anaerobic methanotrophs, represented by both archaea and bacteria, all appear to be engaged in syntrophic interdependencies with other species, to overcome the energetic barriers of methane metabolism in the absence of oxygen. In contrast, aerobic methanotrophy can be carried out by pure cultures of bacteria. Nevertheless, a concept of communal function in aerobic methane oxidation has been gaining momentum, based on data from natural cooccurrence of specific functional guilds, and based on results from laboratory manipulations. The mechanistic details are still sparse on how and why the methanotrophs share their carbon with other species, and whether and what they gain in return. In this minireview we highlight recent studies that led to this new concept of community function in aerobic methane oxidation. We first describe the stable isotope probing experiments employing heavy carbon-labeled methane, tracing methane carbon consumption. We then follow up with analysis of data from microcosm community dynamics. We further discuss the role of a synthetic community approach in unraveling the principles of carbon flow and species cooperation in methane consumption. Finally, we touch on the role of lanthanides, which are rare Earth elements, previously thought to be biologically inert, in bacterial metabolism of methane.