Methanotrophs are organisms which are able to obtain energy by oxidizing methane (CH4). Methane, found widely in nature, is produced in strict anaerobic conditions by methanogenic Archaea (see Methanogens). It is the main gas in anoxic muds, marshes, lakes, rice paddies, and lanfield. Methane is the major constituent of natural gas and is also present in many coal formations. It can be used as an electron donor by methanotrophic bacteria. Methanotrophs can also use other one carbon compounds as a source of energy and carbon. Most of the known methanotrophs are aerobic, although, recently, methanotrophic activities in anoxic environments have been detected. All methanotrophs possess a specific enzyme, methane monooxygenase, which can insert an oxygen atom into the methane molecule generating methanol. The oxygen requirement for the oxygenation of methane explains their obligate aerobic character. The anoxic oxidation of methane requires a consortium of...