Methanotrophy in Extreme Environments

Abstract Methanotrophy is the ability of a few prokaryotes to grow on methane as a sole energy source. Aerobic methanotrophic bacteria are active in natural environments with pH values ranging from 1 to 11, temperatures ranging from 0 to 72°C and salinities up to 30%. In addition, anaerobic methanotrophs are found in permanently cold ocean sediments at temperatures down to −1°C, and in geothermally heated sediments at temperatures up to 90°C. Several extremophilic species of aerobic methanotrophs have been isolated and studied in pure culture, including thermophiles, psychrophiles, acidophiles, alkaliphiles and halophiles. The knowledge of methanotrophs and their ecology in extreme environments is summarized, with particular attention on bacteria with multiple extremophilic phenotypes that are found in acidic subarctic peatlands and in acidic geothermal springs. Key concepts Methane is oxidized by prokaryotes in diverse environments, including some with extreme temperatures, pH values and salinities. The ecology of extremophilic methanotrophs has been studied using cultivation‐independent molecular methods. Extremophilic aerobic methanotrophs have been isolated and studied in pure culture, but anaerobic methanotrophs have not yet been isolated. Some aerobic methanotrophs combine multiple extremophilic phenotypes. Biogeochemical and molecular ecology studies suggest that sulphate‐reducing methanotrophs are capable of living under a similar range of temperatures as are aerobic methanotrophs.