Methanosarcina

Methanosarcina are the only known anaerobic methanogens to produce methane using all three known metabolic pathways for methanogenesis. Most methanogens make methane from carbon dioxide and hydrogen gas. Some others utlize acetate in the acetoclastic pathway. In addition to these two pathways, species of Methanosarcina can also metabolize methylated one-carbon compounds through methylotrophic methanogenesis. Such one-carbon compounds include methylamines, methanol, and methyl thiols. Thus species of Methanosarcina are the most diverse methanogens in terms of physiology. They are found in diverse environments, including trash dumps, sewage heaps, deep see vents, and even in the gut of many different ungulates, including cows, sheep, goats, and deer. Methanosarcina have even been found in the human digestive tract. Methanosarcina are also unique in that they have been found to grow in colonies and even show primitive cellular differentiation. Both M. acetivorans and M. mazei have been found to have exceptionally large genomes. As of August 2006, M. acetivorans possessed the largest sequenced archaeal genome at 5,751,492 bp. Slightly smaller is the genome of M. mazei, with 4,096,345 bp.