Methanotroph

Methanotrophs (sometimes called methanophiles) are prokaryotes that metabolize methane as their source of carbon and chemical energy. They are bacteria or archaea, can grow aerobically or anaerobically, and require single-carbon compounds to survive. Methanotrophs are especially common in or near environments where methane is produced, although some methanotrophs can oxidize atmospheric methane. Their habitats include wetlands, soils, marshes, rice paddies, landfills, aquatic systems (lakes, oceans, streams) and more. They are of special interest to researchers studying global warming, as they play a significant role in the global methane budget, by reducing the amount of methane emitted to the atmosphere. Methanotrophy is a special case of methylotrophy, using single-carbon compounds that are more reduced than carbon dioxide. Some methylotrophs, however, can also make use of multi-carbon compounds; this differentiates them from methanotrophs, which are usually fastidious methane and methanol oxidizers. The only facultative methanotrophs isolated to date are members of the genus Methylocella silvestris, Methylocapsa aurea and several Methylocystis strains. In functional terms, methanotrophs are referred to as methane-oxidizing bacteria. However, methane-oxidizing bacteria encompass other organisms that are not regarded as sole methanotrophs. For this reason, methane-oxidizing bacteria have been separated into subgroups: methane-assimilating bacteria (MAB) groups, the methanotrophs, and autotrophic ammonia-oxidizing bacteria (AAOB), which cooxidize methane. Methanotrophs can be either bacteria or archaea. Which methanotroph species is present is mainly determined by the availability of electron acceptors. Many types of methane oxidizing bacteria (MOB) are known. Differences in the method of formaldehyde fixation and membrane structure divide these bacterial methanotrophs into several groups. There are several subgroups among the methanotrophic archaea.