Methanogens are classified as Archaea.
Methanogens are a type of microorganism that produce methane as a by-product of metabolism under very low oxygen conditions. They are often present in swamps, swamps and other wetlands, where the methane they produce is known as “swamp gas”. Methanogens also exist in the guts of some animals, including cows and humans, where they contribute to the methane content of flatulence. Although once classified as Archaebacteria, methanogens are now classified as Archaea, distinct from Bacteria.
Methanogens can thrive in hot springs.
Some types of methanogen, including those in the genus Methanopyrus, are extremophiles, organisms that thrive in conditions in which most living things could not survive, such as hot springs, hydrothermal vents, hot desert soil, and deep underground environments. Others, such as those in the genus Methanocaldococcus, are mesophilic, meaning they do best at moderate temperatures. Methanobrevibacter smithii is the prominent methanogen in the human intestine, where it helps digest polysaccharides or complex sugars.
Methanogens are rod-shaped or spherical. They do not form a monophyletic group, however, which means that all methanogens do not consist of a single ancestor and all of its descendants. There are over 50 species, all belonging to the Archaea domain. Methanogens do not require oxygen and, in some cases, cannot even survive on oxygen, although they can tolerate its presence for prolonged periods.
Methanogens are a very diverse group. They use a carbon source, such as carbon dioxide or acetate, to drive their metabolism, called methanogenesis, along with hydrogen as a reducing agent. Therefore, they have the ecological benefit of removing excess hydrogen and carbon from anaerobic environments. A methanogen that metabolizes carbon dioxide is classified as a hydrogenotroph, while those that metabolize acetate are called acetotrophs or aceticlastics.
Methanogens play an important ecological role in helping to remove carbon dioxide from the environment. They do this at a substantial price, however, as the process of methanogenesis also produces methane, which has a global warming potential 21 times that of carbon dioxide. Fortunately, this effect can be offset by using methane as a biofuel.