They live in diverse environments where they can remain safe from the effects of oxygen, whether on the earth's surface, in groundwater, in deep sea vents, and in animal digestive tracts.
Primitive versions of hemoglobin have been found in M. acetivorans, suggesting the microbe or an ancestor of it may have played a crucial role in the evolution of life on Earth.
The theory suggests that acquisition of a new metabolic pathway via gene transfer followed by exponential reproduction allowed the microbe to rapidly consume vast deposits of organic carbon in marine sediments, leading to a sharp buildup of methane and carbon dioxide in the Earth's oceans and atmosphere that killed around 90% of the world's species.
Methanogenesis is critical to the waste-treatment industry and biologically produced methane also represents an important alternative fuel source.
[5] Earlier research by the team had shown that a gene in M. barkeri had an in-frame amber (UAG) codon that did not signal the end of a protein, as would normally be expected.
This behavior suggested the possibility of an unknown amino acid which was confirmed over several years by slicing the protein into peptides and sequencing them.
[7][8] The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[9] and National Center for Biotechnology Information (NCBI).
M. frisia, M. soligelidi) M. acetivorans M. siciliae M. flavescens M. thermophila M. spelaei M. barkeri M. vacuolata Species incertae sedis:
[17] Inspired by M. acetivorans, a team of Penn State researchers led by James G. Ferry and Christopher House proposed a new "thermodynamical theory of evolution" in 2006.
The authors observed that though the "debate between the heterotrophic and chemotrophic theories revolved around carbon fixation", in actuality "these pathways evolved first to make energy.
"[2] The scientists further proposed mechanisms which would have allowed the mineral-bound proto-cell to become free-living and for the evolution of acetate metabolism into methane, using the same energy-based pathways.
[2] Recently researchers have proposed an evolution hypothesis for acetate kinase and phosphoacetyl transferase with genomic evidence from Methanosarcina.
[20] Evidence suggests acetate kinase evolved in an ancient halophilic Methanosarcina genome through duplication and divergence of the acetyl coA synthetase gene.
[23] The scientists concluded that these new genes, combined with widely available organic carbon deposits in the ocean and a plentiful supply of nickel,[b] allowed Methanosarcina populations to increase dramatically.
It is possible the buildup of carbon dioxide and methane in the atmosphere eventually caused the release of hydrogen sulfide gas, further stressing terrestrial life.
[22] The microbe theory suggests that volcanic activity played a different role - supplying the nickel which Methanosarcina required as a cofactor.
[25] In 1985, Shimizu Construction developed a bioreactor that uses Methanosarcina to treat waste water from food processing plants and paper mills.
[26] According to a 1994 report in Chemistry and Industry, bioreactors utilizing anaerobic digestion by Methanothrix soehngenii or Methanosarcina produced less sludge byproduct than aerobic counterparts.