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Methanogens are microorganisms that produce methane as a metabolic byproduct in hypoxic conditions. They belong to the domain Archaea and are members of the phylum Euryarchaeota. Methanogens are common in wetlands, where they are responsible for marsh gas, and can occur in the digestive tracts of animals including ruminants and humans, where they are responsible for the methane content of belching and flatulence. In marine sediments, the biological production of methane, termed methanogenesis, is generally confined to where sulfates are depleted below the top layers and methanogens play an indispensable role in anaerobic wastewater treatments. Other methanogens are extremophiles, found in environments such as hot springs and submarine hydrothermal vents as well as in the "solid" rock of Earth's crust, kilometers below the surface.
In biology, syntrophy, syntrophism, or cross-feeding is the cooperative interaction between at least two microbial species to degrade a single substrate. This type of biological interaction typically involves the transfer of one or more metabolic intermediates between two or more metabolically diverse microbial species living in close proximity to each other. Thus, syntrophy can be considered an obligatory interdependency and a mutualistic metabolism between different microbial species, wherein the growth of one partner depends on the nutrients, growth factors, or substrates provided by the other(s).
Methanogenium boonei is a methanogenic archaean. Cells are non-motile irregular cocci 1.0–2.5 μm in diameter. This mesophile grows optimally at 19.4 °C, pH6.4–7.8, salinity 0.3–0.5M Na+. It was first isolated from Skan Bay, Alaska.
In taxonomy, Methanohalophilus is a genus of the Methanosarcinaceae.
Archaeol is composed of two phytanyl chains linked to the sn-2 and sn-3 positions of glycerol. As its phosphate ester, it is a common component of the membranes of archaea.
Methanocaldococcus jannaschii is a thermophilic methanogenic archaean in the class Methanococci. It was the first archaeon, and third organism, to have its complete genome sequenced. The sequencing identified many genes unique to the archaea. Many of the synthesis pathways for methanogenic cofactors were worked out biochemically in this organism, as were several other archaeal-specific metabolic pathways.
Methanobrevibacter cuticularis is a species of methanogen archaeon. It was first isolated from the hindgut of the termite Reticulitermes flavipes. It is rod-shaped, ranging in size from 0.34 to 1.6 µm and possesses polar fibers. Its morphology, gram-positive staining reaction, resistance to cell lysis by chemical agents and narrow range of utilizable substrates are typical of species belonging to the family Methanobacteriaceae. It habitates on or near the hindgut epithelium and also attached to filamentous prokaryotes associated with the gut wall. It is one of the predominant gut biota.
Methanobrevibacter curvatus is a species of methanogen archaeon. It was first isolated from the hindgut of the termite Reticulitermes flavipes. It is rod-shaped, ranging in size from 0.34 to 1.6 µm and possesses polar fibers. Its morphology, gram-positive staining reaction, resistance to cell lysis by chemical agents and narrow range of utilisable substrates are typical of species belonging to the family Methanobacteriaceae. It habitates on or near the hindgut epithelium and also attached to filamentous prokaryotes associated with the gut wall. It is one of the predominant gut biota.
Methanobrevibacter woesei is a species of methanogen archaeon, named after Carl R. Woese.
Methanococcoides burtonii is a methylotrophic methanogenic archaeon first isolated from Ace Lake, Antarctica. Its type strain is DSM 6242.
Methanolobus tindarius is a methanogen archaeon. It is marine, mesophilic, coccoid, lobal and monotrichous flagellated. They were isolated from coastal sediments.
Methanosarcina thermophila is a thermophilic, acetotrophic, methane-producing archaeon.
Methanococcus maripaludis is a species of methanogenic archaea found in marine environments, predominantly salt marshes. M. maripaludis is a weakly motile, non-spore-forming, Gram-negative, strict anaerobic mesophile with a pleomorphic coccoid-rod shape, averaging 1.2 by 1.6 μm is size. The genome of M. maripaludis has been sequenced, and over 1,700 protein-coding genes have been identified. In ideal conditions, M. maripaludis grows quickly and can double every two hours.
Methanococcoides methylutens is a methylotrophic marine methanogen, the type species of its genus. It utilises trimethylamine, diethylamine, monomethylamine, and methanol as substrates for growth and methanogenesis. Cells are non-motile, non-spore-forming, irregular cocci 1 μm in diameter which stain Gram-negative and occur singly or in pairs. TMA-10 is the type strain.
Methanohalophilus mahii is an obligately anaerobic, methylotrophic, methanogenic cocci-shaped archaeon of the genus Methanohalophilus that can be found in high salinity aquatic environments. The name Methanohalophilus is said to be derived from methanum meaning "methane" in Latin; halo meaning "salt" in Greek; and mahii meaning "of Mah" in Latin, after R.A. Mah, who did substantial amounts of research on aerobic and methanogenic microbes. The proper word in ancient Greek for "salt" is however hals (ἅλς). The specific strain type was designated SLP and is currently the only identified strain of this species.
Methanomethylovorans hollandica is a species of methylotrophic methanogen able to grow on dimethyl sulfide and methanethiol. It is the type species of its genus. It is obligately anaerobic. It was the first strictly anaerobic archeaon isolated from freshwater sediments in which dimethyl sulfide is the sole source of carbon. It is not a halophile. It can use methyl compounds as substrates, but it cannot use carbon dioxide or acetate. Because dimethyl sulfide has implications with respect to global warming, this organism may be of considerable importance.
Methanosarcina barkeri is the most fundamental species of the genus Methanosarcina, and their properties apply generally to the genus Methanosarcina. Methanosarcina barkeri can produce methane anaerobically through different metabolic pathways. M. barkeri can subsume a variety of molecules for ATP production, including methanol, acetate, methylamines, and different forms of hydrogen and carbon dioxide. Although it is a slow developer and is sensitive to change in environmental conditions, M. barkeri is able to grow in a variety of different substrates, adding to its appeal for genetic analysis. Additionally, M. barkeri is the first organism in which the amino acid pyrrolysine was found. Furthermore, two strains of M. barkeri, M. b. Fusaro and M. b. MS have been identified to possess an F-type ATPase along with an A-type ATPase.
Methanobrevibacter oralis is a methanogenic archaeon species considered to be a member of the human microbiota, mainly associated to the oral cavity. M. oralis is a coccobacillary shaped, single-cell, Gram-positive, non-motile microorganism of the Archaea domain of life. This species has been isolated and sequenced from humans in dental plaque and in their gastrointestinal tract. As a methanogen and a hydrogenotroph, this prokaryote can produce methane by using hydrogen and carbon dioxide as substrates through a process called methanogenesis.
Formatotrophs are organisms that can assimilate formate or formic acid to use as a carbon source or for reducing power. Some authors classify formatotrophs as one of the five trophic groups of methanogens, which also include hydrogenotrophs, acetotrophs, methylotrophs, and alcoholotrophs. Formatotrophs have garnered attention for applications in biotechnology as part of a "formate bioeconomy" in which synthesized formate could be used as a nutrient for microoganisms. Formate can be electrochemically synthesized from CO2 and renewable energy, and formatotrophs may be genetically modified to enhance production of biochemical products to be used as biofuels. Technical limitations in culturing formatotrophs have limited the discovery of natural formatotrophs and impeded research on their formate-metabolizing enzymes, which are of interest for applications in carbon sequestration and astrobiology.
References
- ↑ Mochimaru, H.; Tamaki, H.; Hanada, S.; Imachi, H.; Nakamura, K.; Sakata, S.; Kamagata, Y. (2009). "Methanolobus profundi sp. nov., a methylotrophic methanogen isolated from deep subsurface sediments in a natural gas field". International Journal of Systematic and Evolutionary Microbiology. 59 (4): 714–718. doi: 10.1099/ijs.0.001677-0 . ISSN 1466-5026. PMID 19329594.
- ↑ Sue-Yao Wu; Mei-Chin Lai (10 December 2010). "Methanogenic Archaea Isolated from Taiwan's Chelungpu Fault". Appl. Environ. Microbiol. 27 (3): 830–838. doi: 10.1128/AEM.01539-10 . PMC 3028716 . PMID 21148697. S2CID 5183722 . Retrieved 2017-12-12.
