Methanogen

Not to be confused with Methanotroph.

Methanogens are anaerobic archaea that produce methane as a byproduct of their energy metabolism, i.e., catabolism. Methane production, or methanogenesis, is the only biochemical pathway for ATP generation in methanogens. All known methanogens belong exclusively to the domain Archaea, although some bacteria, plants, and animal cells are also known to produce methane.^[1] However, the biochemical pathway for methane production in these organisms differs from that in methanogens and does not contribute to ATP formation. Methanogens belong to various phyla within the domain Archaea. Previous studies placed all known methanogens into the superphylum Euryarchaeota.^[2][3] However, recent phylogenomic data have led to their reclassification into several different phyla.^[4] Methanogens are common in various anoxic environments, such as marine and freshwater sediments, wetlands, the digestive tracts of animals, wastewater treatment plants, rice paddy soil, and landfills.^[5] While some methanogens are extremophiles, such as Methanopyrus kandleri, which grows between 84 and 110°C,^[6] or Methanonatronarchaeum thermophilum, which grows at a pH range of 8.2 to 10.2 and a Na⁺ concentration of 3 to 4.8 M,^[7] most of the isolates are mesophilic and grow around neutral pH.^[8]

Physical description

Methanogens are usually cocci (spherical) or rods (cylindrical) in shape, but long filaments (Methanobrevibacter filliformis, Methanospirillum hungatei) and curved forms (Methanobrevibacter curvatus, Methanobrevibacter cuticularis) also occur. There are over 150 described species of methanogens,^[9] which do not form a monophyletic group in the phylum Euryarchaeota (see Taxonomy). They are exclusively anaerobic organisms that cannot function under aerobic conditions due to the extreme oxygen sensitivity of methanogenesis enzymes and FeS clusters involved in ATP production. However, the degree of oxygen sensitivity varies, as methanogenesis has often been detected in temporarily oxygenated environments such as rice paddy soil,^[10][11][12] and various molecular mechanisms potentially involved in oxygen and reactive oxygen species (ROS) detoxification have been proposed.^[13] For instance, a recently identified species Candidatus Methanothrix paradoxum common in wetlands and soil can function in anoxic microsites within aerobic environments^[14] but it is sensitive to the presence of oxygen even at trace level and cannot usually sustain oxygen stress for a prolonged time. However, Methanosarcina barkeri from a sister family Methanosarcinaceae is exceptional in possessing a superoxide dismutase (SOD) enzyme, and may survive longer than the others in the presence of O₂.^[3]

As is the case for other archaea, methanogens lack peptidoglycan, a polymer that is found in the cell walls of bacteria.^[15] Instead, some methanogens have a cell wall formed by pseudopeptidoglycan (also known as pseudomurein). Other methanogens have a paracrystalline protein array (S-layer) that fits together like a jigsaw puzzle.^[5] In some lineages there are less common types of cell envelope such as the proteinaceous sheath of Methanospirillum or the methanochondroitin of Methanosarcina aggregated cells.^[16]

Ecology

In anaerobic environments, methanogens play a vital ecological role, removing excess hydrogen and fermentation products that have been produced by other forms of anaerobic respiration.^[17] Methanogens typically thrive in environments in which all electron acceptors other than CO₂ (such as oxygen, nitrate, ferric iron (Fe(III)), and sulfate) have been depleted. Such environments include wetlands and rice paddy soil, the digestive tracts of various animals (ruminants, arthropods, humans),^[18][19][20] wastewater treatment plants and landfills, deep-water oceanic sediments, and hydrothermal vents.^[21] Most of these environments are not categorized as extreme, and thus the methanogens inhabiting them are also not considered extremophiles. However, many well-studied methanogens are thermophiles such as Methanopyrus kandleri, Methanothermobacter marburgensis, Methanocaldococcus jannaschii. On the other hand, gut methanogens such as Methanobrevibacter smithii common in humans or Methanobrevibacter ruminantium omnipresent in ruminants are mesophiles.

Methanogens in extreme environments

In deep basaltic rocks near the mid-ocean ridges, methanogens can obtain their hydrogen from the serpentinization reaction of olivine as observed in the hydrothermal field of Lost City. The thermal breakdown of water and water radiolysis are other possible sources of hydrogen. Methanogens are key agents of remineralization of organic carbon in continental margin sediments and other aquatic sediments with high rates of sedimentation and high sediment organic matter. Under the correct conditions of pressure and temperature, biogenic methane can accumulate in massive deposits of methane clathrates^[22] that account for a significant fraction of organic carbon in continental margin sediments and represent a key reservoir of a potent greenhouse gas.^[23]

Methanogens have been found in several extreme environments on Earth – buried under kilometres of ice in Greenland and living in hot, dry desert soil. They are known to be the most common archaea in deep subterranean habitats. Live microbes making methane were found in a glacial ice core sample retrieved from about three kilometres under Greenland by researchers from the University of California, Berkeley. They also found a constant metabolism able to repair macromolecular damage, at temperatures of 145 to –40 °C.^[6]

Another study^[7] has also discovered methanogens in a harsh environment on Earth. Researchers studied dozens of soil and vapour samples from five different desert environments in Utah, Idaho and California in the United States, and in Canada and Chile. Of these, five soil samples and three vapour samples from the vicinity of the Mars Desert Research Station in Utah were found to have signs of viable methanogens.^[8]

Some scientists have proposed that the presence of methane in the Martian atmosphere may be indicative of native methanogens on that planet.^[24] In June 2019, NASA's Curiosity rover detected methane, commonly generated by underground microbes such as methanogens, which signals possibility of life on Mars.^[25]

Closely related to the methanogens are the anaerobic methane oxidizers, which utilize methane as a substrate in conjunction with the reduction of sulfate and nitrate.^[26] Most methanogens are autotrophic producers, but those that oxidize CH₃COO⁻ are classed as chemotroph instead.

Methanogens in the digestive tract of animals

The digestive tract of animals is characterized by a nutrient-rich and predominantly anaerobic environment, making it an ideal habitat for many microbes, including methanogens. Despite this, methanogens and archaea, in general, were largely overlooked as part of the gut microbiota until recently. However, they play a crucial role in maintaining gut balance by utilizing end products of bacterial fermentation, such as H₂, acetate, methanol, and methylamines.

Recent extensive surveys of archaea presence in the animal gut, based on 16S rRNA analysis, have provided a comprehensive view of archaea diversity and abundance.^[27][28][29] These studies revealed that only a few archaeal lineages are present, with the majority being methanogens, while non-methanogenic archaea are rare and not abundant. Taxonomic classification of archaeal diversity identified that representatives of only three phyla are present in the digestive tracts of animals: Methanobacteriota (order Methanobacteriales), Thermoplasmatota (order Methanomassiliicoccales), and Halobacteriota (orders Methanomicrobiales and Methanosarcinales). However, not all families and genera within these orders were detected in animal guts, but only a few genera, suggesting their specific adaptations to the gut environment.

Comparative genomics and molecular signatures

Comparative proteomic analysis has led to the identification of 31 signature proteins which are specific for methanogens (also known as Methanoarchaeota). Most of these proteins are related to methanogenesis, and they could serve as potential molecular markers for methanogens. Additionally, 10 proteins found in all methanogens, which are shared by Archaeoglobus, suggest that these two groups are related. In phylogenetic trees, methanogens are not monophyletic and they are generally split into three clades. Hence, the unique shared presence of large numbers of proteins by all methanogens could be due to lateral gene transfers.^[30] Additionally, more recent novel proteins associated with sulfide trafficking have been linked to methanogen archaea.^[31] More proteomic analysis is needed to further differentiate specific genera within the methanogen class and reveal novel pathways for methanogenic metabolism.

Modern DNA or RNA sequencing approaches has elucidated several genomic markers specific to several groups of methanogens. One such finding isolated nine methanogens from genus Methanoculleus and found that there were at least 2 trehalose synthases genes that were found in all nine genomes.^[32] Thus far, the gene has been observed only in this genus, therefore it can be used as a marker to identify the archaea Methanoculleus. As sequencing techniques progress and databases become populated with an abundance of genomic data, a greater number of strains and traits can be identified, but many genera have remained understudied. For example, halophilic methanogens are potentially important microbes for carbon cycling in coastal wetland ecosystems but seem to be greatly understudied. One recent publication isolated a novel strain from genus Methanohalophilus which resides in sulfide-rich seawater. Interestingly, they have isolated several portions of this strain's genome that are different from other isolated strains of this genus (Methanohalophilus mahii, Methanohalophilus halophilus, Methanohalophilus portucalensis, Methanohalophilus euhalbius). Some differences include a highly conserved genome, sulfur and glycogen metabolisms and viral resistance.^[33] Genomic markers consistent with the microbes environment have been observed in many other cases. One such study found that methane producing archaea found in hydraulic fracturing zones had genomes which varied with vertical depth. Subsurface and surface genomes varied along with the constraints found in individual depth zones, though fine-scale diversity was also found in this study.^[34] Genomic markers pointing at environmentally relevant factors are often non-exclusive. A survey of Methanogenic Thermoplasmata has found these organisms in human and animal intestinal tracts. This novel species was also found in other methanogenic environments such as wetland soils, though the group isolated in the wetlands did tend to have a larger number of genes encoding for anti-oxidation enzymes that were not present in the same group isolated in the human and animal intestinal tract.^[35] A common issue with identifying and discovering novel species of methanogens is that sometimes the genomic differences can be quite small, yet the research group decides they are different enough to separate into individual species. One study took a group of Methanocellales and ran a comparative genomic study. The three strains were originally considered identical, but a detailed approach to genomic isolation showed differences among their previously considered identical genomes. Differences were seen in gene copy number and there was also metabolic diversity associated with the genomic information.^[36]

Genomic signatures not only allow one to mark unique methanogens and genes relevant to environmental conditions; it has also led to a better understanding of the evolution of these archaea. Some methanogens must actively mitigate against oxic environments. Functional genes involved with the production of antioxidants have been found in methanogens, and some specific groups tend to have an enrichment of this genomic feature. Methanogens containing a genome with enriched antioxidant properties may provide evidence that this genomic addition may have occurred during the Great Oxygenation Event.^[37] In another study, three strains from the lineage Thermoplasmatales isolated from animal gastro-intestinal tracts revealed evolutionary differences. The eukaryotic-like histone gene which is present in most methanogen genomes was not present, alluding to evidence that an ancestral branch was lost within Thermoplasmatales and related lineages.^[38] Furthermore, the group Methanomassiliicoccus has a genome which appears to have lost many common genes coding for the first several steps of methanogenesis. These genes appear to have been replaced by genes coding for a novel methylated methogenic pathway. This pathway has been reported in several types of environments, pointing to non-environment specific evolution, and may point to an ancestral deviation.^[39]

Metabolism

Methane production

Methanogens are known to produce methane from substrates such as H₂/CO₂, acetate, formate, methanol and methylamines in a process called methanogenesis.^[40] Different methanogenic reactions are catalyzed by unique sets of enzymes and coenzymes. While reaction mechanism and energetics vary between one reaction and another, all of these reactions contribute to net positive energy production by creating ion concentration gradients that are used to drive ATP synthesis.^[41] The overall reaction for H₂/CO₂ methanogenesis is:

${\displaystyle {\ce {CO2 + 4 H2 -> CH4 + 2 H2O}}}$ (∆G˚’ = -134 kJ/mol CH₄)

Well-studied organisms that produce methane via H₂/CO₂ methanogenesis include Methanosarcina barkeri, Methanobacterium thermoautotrophicum, and Methanobacterium wolfei.^[42][43][44] These organisms are typically found in anaerobic environments.^[40]

In the earliest stage of H₂/CO₂ methanogenesis, CO₂ binds to methanofuran (MF) and is reduced to formyl-MF. This endergonic reductive process (∆G˚’= +16 kJ/mol) is dependent on the availability of H₂ and is catalyzed by the enzyme formyl-MF dehydrogenase.^[40]

${\displaystyle {\ce {CO2 + H2 + MF -> HCO-MF + H2O}}}$

The formyl constituent of formyl-MF is then transferred to the coenzyme tetrahydromethanopterin (H4MPT) and is catalyzed by a soluble enzyme known as formyltransferase. This results in the formation of formyl-H4MPT.^[40]

${\displaystyle {\ce {HCO-MF + H4MPT -> HCO-H4MPT + MF}}}$

Formyl-H4MPT is subsequently reduced to methenyl-H4MPT. Methenyl-H4MPT then undergoes a one-step hydrolysis followed by a two-step reduction to methyl-H4MPT. The two-step reversible reduction is assisted by coenzyme F₄₂₀ whose hydride acceptor spontaneously oxidizes.^[40] Once oxidized, F₄₂₀’s electron supply is replenished by accepting electrons from H₂. This step is catalyzed by methylene H4MPT dehydrogenase.^[45]

${\displaystyle {\ce {HCO-H4MPT + H+ -> CH-H4MPT+ + H2O}}}$ (Formyl-H4MPT reduction)

${\displaystyle {\ce {CH-H4MPT+ + F420H2 -> CH2=H4MPT + F420 + H+}}}$(Methenyl-H4MPT hydrolysis)

${\displaystyle {\ce {CH2=H4MPT + H2 -> CH3-H4MPT + H+}}}$(H4MPT reduction)

Next, the methyl group of methyl-M4MPT is transferred to coenzyme M via a methyltransferase-catalyzed reaction.^[46][47]

${\displaystyle {\ce {CH3-H4MPT + HS-CoM -> CH3-S-CoM + H4MPT}}}$

The final step of H₂/CO₂ methanogenic involves methyl-coenzyme M reductase and two coenzymes: N-7 mercaptoheptanoylthreonine phosphate (HS-HTP) and coenzyme F₄₃₀. HS-HTP donates electrons to methyl-coenzyme M allowing the formation of methane and mixed disulfide of HS-CoM.^[48] F₄₃₀, on the other hand, serves as a prosthetic group to the reductase. H₂ donates electrons to the mixed disulfide of HS-CoM and regenerates coenzyme M.^[49]

${\displaystyle {\ce {CH3-S-CoM + HS-HTP -> CH4 + CoM-S-S-HTP}}}$ (Formation of methane)

${\displaystyle {\ce {CoM-S-S-HTP + H2 -> HS-CoM + HS-HTP}}}$ (Regeneration of coenzyme M)

Biotechnological application

Wastewater treatment

Methanogens are widely used in anaerobic digestors to treat wastewater as well as aqueous organic pollutants. Industries have selected methanogens for their ability to perform biomethanation during wastewater decomposition thereby rendering the process sustainable and cost-effective.^[50]

Bio-decomposition in the anaerobic digester involves a four-staged cooperative action performed by different microorganisms.^[51] The first stage is the hydrolysis of insoluble polymerized organic matter by anaerobes such as Streptococcus and Enterobacterium.^[52] In the second stage, acidogens break down dissolved organic pollutants in wastewater to fatty acids. In the third stage, acetogens convert fatty acids to acetates. In the final stage, methanogens metabolize acetates to gaseous methane. The byproduct methane leaves the aqueous layer and serves as an energy source to power wastewater-processing within the digestor, thus generating a self-sustaining mechanism.^[53]

Methanogens also effectively decrease the concentration of organic matter in wastewater run-off.^[54] For instance, agricultural wastewater, highly rich in organic material, has been a major cause of aquatic ecosystem degradation. The chemical imbalances can lead to severe ramifications such as eutrophication. Through anaerobic digestion, the purification of wastewater can prevent unexpected blooms in water systems as well as trap methanogenesis within digesters. This allocates biomethane for energy production and prevents a potent greenhouse gas, methane, from being released into the atmosphere.

The organic components of wastewater vary vastly. Chemical structures of the organic matter select for specific methanogens to perform anaerobic digestion. An example is the members of Methanosaeta genus dominate the digestion of palm oil mill effluent (POME) and brewery waste.^[54] Modernizing wastewater treatment systems to incorporate higher diversity of microorganisms to decrease organic content in treatment is under active research in the field of microbiological and chemical engineering.^[55] Current new generations of Staged Multi-Phase Anaerobic reactors and Upflow Sludge Bed reactor systems are designed to have innovated features to counter high loading wastewater input, extreme temperature conditions, and possible inhibitory compounds.^[56]

Taxonomy

Initially, methanogens were considered to be bacteria, as it was not possible to distinguish archaea and bacteria before the introduction of molecular techniques such as DNA sequencing and PCR. Since the introduction of the domain Archaea by Carl Woese in 1977,^[57] methanogens were for a prolonged period considered a monophyletic group, later named Euryarchaeota (super)phylum. However, intensive studies of various environments have proved that there are more and more non-methanogenic lineages among methanogenic ones.

The development of genome sequencing directly from environmental samples (metagenomics) allowed the discovery of the first methanogens outside the Euryarchaeota superphylum. The first such putative methanogenic lineage was Bathyarchaeia,^[58] a class within the Thermoproteota phylum. Later, it was shown that this lineage is not methanogenic but alkane-oxidizing utilizing highly divergent enzyme Acr similar to the hallmark gene of methanogenesis, methyl-CoM reductase (McrABG).^[59] The first isolate of Bathyarchaeum tardum from sediment of coastal lake in Russia showed that it metabolizes aromatic compounds and proteins^[60] as it was previously predicted based on metagenomic studies.^[61][62][63] However, more new putative methanogens outside of Euryarchaeota were discovered based on the presence McrABG.

For instance, methanogens were found in the phyla Thermoproteota (orders Methanomethyliales, Korarchaeales, Methanohydrogenales, Nezhaarchaeales) and Methanobacteriota_B (order Methanofastidiosales). Additionally, some new lineages of methanogens were isolated in pure culture, which allowed the discovery of a new type of methanogenesis: H₂-dependent methyl-reducing methanogenesis, which is independent of the Wood-Ljungdahl pathway. For example, in 2012, the order Methanoplasmatales from the phylum Thermoplasmatota was described as a seventh order of methanogens.^[64] Later, the order was renamed Methanomassiliicoccales based on the isolated from human gut Methanomassiliicoccus luminyensis.^[65][66]

Another new lineage in the Halobacteriota phylum, order Methanonatronarchaeales, was discovered in alkaline saline lakes in Siberia in 2017.^[67][68] It also employs H₂-dependent methyl-reducing methanogenesis but intriguingly harbors almost the full Wood-Ljungdahl pathway. However, it is disconnected from McrABG as no MtrA-H complex was detected.^[69][70]

The taxonomy of methanogens reflects the evolution of these archaea, with some studies suggesting that the Last Archaeal Common Ancestor was methanogenic.^[71] If correct, this suggests that many archaeal lineages lost the ability to produce methane and switched to other types of metabolism. Currently, most of the isolated methanogens belong to one of three archaeal phyla (classification GTDB release 220): Halobacteriota, Methanobacteriota, and Thermoplasmatota. Under the International Code of Nomenclature for Prokaryotes,^[72] all three phyla belong to the same kingdom, Methanobacteriati.^[73][74] In total, more than 150 methanogen species are known in culture, with some represented by more than one strain.^[75]

Phylum Halobacteriota

Class Methanocellia

Order Methanocellales

Family Methanocellaceae

Genus Methanocella Sakai et al. 2008

Methanocella paludicola Sakai et al. 2008 (type species)

Methanocella arvoryzae Sakai et al. 2010

Methanocella conradii Lü and Lu 2012

Class Methanomicrobia

Order Methanomicrobiales

Family Methanocalculaceae Zhilina et al. 2014

Family Methanocorpusculaceae Zellner et al. 1989

Methanocorpusculum Zellner et al. 1988

Methanocorpusculum parvum Zellner et al. 1988 (type species)

Methanocorpusculum bavaricum Zellner et al. 1989

Methanocorpusculum labreanum

Methanocorpusculum sinense Zellner et al. 1989

Family Methanomicrobiaceae Balch and Wolfe 1981

Genus Methanomicrobium Balch and Wolfe 1981

Methanomicrobium mobile (Paynter and Hungate 1968) Balch and Wolfe 1981 (type species)

Methanomicrobium antiquum Mochimaru et al. 2016

Genus Methanoculleus Maestrojuán et al. 1990

Methanoculleus bourgensis corrig. (Ollivier et al. 1986) Maestrojuán et al. 1990 (type species)

Methanoculleus chikugoensis Dianou et al. 2001

Methanoculleus horonobensis Shimizu et al. 2013

Methanoculleus hydrogenitrophicus Tian et al. 2010

Methanoculleus marisnigri

Methanoculleus palmolei Zellner et al. 1998

Methanoculleus receptaculi Cheng et al. 2008

Methanoculleus sediminis Chen et al. 2015

Methanoculleus submarinus Mikucki et al. 2003

Methanoculleus taiwanensis Weng et al. 2015

Methanoculleus thermophilus corrig. (Rivard and Smith 1982) Maestrojuán et al. 1990

Genus Methanogenium Romesser et al. 1981

Methanogenium cariaci Romesser et al. 1981 (type species)

Methanogenium frigidum

Methanogenium marinum Chong et al. 2003

Methanogenium organophilum

Genus Methanofollis Zellner et al. 1999

Methanofollis tationis (Zabel et al. 1986) Zellner et al. 1999 (type strains)

Methanofollis aquaemaris Lai and Chen 2001

Methanofollis ethanolicus Imachi et al. 2009

Methanofollis fontis Chen et al. 2020

Methanofollis formosanus Wu et al. 2005

Methanofollis liminatans (Zellner et al. 1990) Zellner et al. 1999

Family Methanoregulaceae Sakai et al. 2012

Genus Methanoregula Bräuer et al. 2011

Methanoregula boonei Bräuer et al. 2011 (type species)

Methanoregula formicica Yashiro et al. 2011

Family Methanospirillaceae Boone et al. 2002

Methanospirillum Ferry et al. 1974

'Methanospirillum hungatei corrig. Ferry et al. 1974 (type species)

Methanospirillum lacunae Iino et al. 2010

Methanospirillum psychrodurum Zhou et al. 2014

Methanospirillum stamsii Parshina et al. 2014

Class Methanonatronarchaeia

Order Methanonatronarchaeales

Family Methanonatronarchaeaceae Sorokin et al. 2018

Genus Methanonatronarchaeum Sorokin et al. 2018

Methanonatronarchaeum thermophilum Sorokin et al. 2018 (type species)

Class Methanosarcinia

Order Methanosarcinales

Family Methanosarcinaceae

Genus Methanosarcina Kluyver and van Niel 1936

Methanosarcina barkeri Schnellen 1947 (type species)

Methanosarcina acetivorans

Methanosarcina baltica von Klein et al. 2002

Methanosarcina flavescens Kern et al. 2016

Methanosarcina horonobensis Shimizu et al. 2011

Methanosarcina lacustris Simankova et al. 2002

Methanosarcina mazei (Barker 1936) Mah and Kuhn 1984

Methanosarcina semesiae Lyimo et al. 2000

Methanosarcina siciliae (Stetter and König 1989) Ni et al. 1994

Methanosarcina soligelidi Wagner et al. 2013

Methanosarcina spelaei Ganzert et al. 2014

Methanosarcina subterranea Shimizu et al. 2015

Methanosarcina thermophila Zinder et al. 1985

Methanosarcina vacuolata Zhilina and Zavarzin 1987

Genus Methanimicrococcus corrig. Sprenger et al. 2000

Methanimicrococcus blatticola corrig. Sprenger et al. 2000

Genus Methanococcoides Sowers and Ferry 1985

Methanococcoides methylutens Sowers and Ferry 1985 (type species)

Methanococcoides alaskense Singh et al. 2005

Methanococcoides burtonii Franzmann et al. 1993

Methanococcoides orientis Liang et al. 2022

Methanococcoides vulcani L'Haridon et al. 2014

Genus Methanohalobium Zhilina and Zavarzin 1988

Methanohalobium evestigatum corrig. Zhilina and Zavarzin 1988 (type species)

Genus Methanohalophilus Paterek and Smith 1988

Methanohalophilus mahii Paterek and Smith 1988 (type species)

Methanohalophilus halophilus (Zhilina 1984) Wilharm et al. 1991

Methanohalophilus levihalophilus Katayama et al. 2014

Methanohalophilus portucalensis Boone et al. 1993

Methanohalophilus profundi L'Haridon et al. 2021

Genus Methanolobus König and Stetter 1983

Methanolobus tindarius König and Stetter 1983 (type species)

Methanolobus bombayensis Kadam et al. 1994

Methanolobus chelungpuianus Wu and Lai 2015

Methanolobus halotolerans Shen et al. 2020

Methanolobus mangrovi Zhou et al. 2023

Methanolobus oregonensis (Liu et al. 1990) Boone 2002

Methanolobus profundi Mochimaru et al. 2009

Methanolobus psychrotolerans Chen et al. 2018

Methanolobus sediminis Zhou et al. 2023

Methanolobus taylorii Oremland and Boone 1994

Methanolobus vulcani Stetter et al. 1989

Methanolobus zinderi Doerfert et al. 2009

Genus Methanomethylovorans Lomans et al. 2004

Methanomethylovorans hollandica Lomans et al. 2004 (type species)

Methanomethylovorans thermophila Jiang et al. 2005

Methanomethylovorans uponensis Cha et al. 2014

Genus Methanosalsum Boone and Baker 2002

Methanosalsum zhilinae (Mathrani et al. 1988) Boone and Baker 2002 (type species)

Methanosalsum natronophilum Sorokin et al. 2015

Family Methanotrichaceae

Genus Methanothrix Huser et al. 1983

Methanothrix soehngenii Huser et al. 1983 (type species)

Methanothrix harundinacea (Ma et al. 2006) Akinyemi et al. 2021

Methanothrix thermoacetophila corrig. Nozhevnikova and Chudina 1988

"Candidatus Methanothrix paradoxa" corrig. Angle et al. 2017

Family Methermicoccaceae

Genus Methermicoccus Cheng et al. 2007

Methermicoccus shengliensis Cheng et al. 2007 (type species)

Phylum Methanobacteriota

Class Methanobacteria

Order Methanobacteriales

Family Methanobacteriaceae

Genus Methanobacterium Kluyver and van Niel 1936

Methanobacterium formicicum Schnellen 1947 (type species)

Methanobacterium bryantii

Genus Methanobrevibacter Balch and Wolfe 1981

Methanobrevibacter ruminantium (Smith and Hungate 1958) Balch and Wolfe 1981 (type species)

Methanobrevibacter acididurans Savant et al. 2002

Methanobrevibacter arboriphilus corrig. (Zeikus and Henning 1975) Balch and Wolfe 1981

Methanobrevibacter boviskoreani Lee et al. 2013

Methanobrevibacter curvatus Leadbetter and Breznak 1997

Methanobrevibacter cuticularis Leadbetter and Breznak 1997

Methanobrevibacter filiformis Leadbetter et al. 1998

Methanobrevibacter gottschalkii Miller and Lin 2002

Methanobrevibacter millerae Rea et al. 2007

Methanobrevibacter olleyae Rea et al. 2007

Methanobrevibacter oralis Ferrari et al. 1995

Methanobrevibacter smithii Balch and Wolfe 1981

Methanobrevibacter thaueri Miller and Lin 2002

Methanobrevibacter woesei Miller and Lin 2002

Methanobrevibacter wolinii Miller and Lin 2002

"Methanobrevibacter massiliense" Huynh et al. 2015

"Candidatus Methanobrevibacter intestini" Chibani et al. 2022

Genus Methanosphaera Miller and Wolin 1985

Methanosphaera stadtmanae corrig. Miller and Wolin 1985 (type species)

Methanosphaera cuniculi Biavati et al. 1990

Genus Methanothermobacter Wasserfallen et al. 2000

Methanothermobacter thermautotrophicus corrig. (Zeikus and Wolfe 1972) Wasserfallen et al. 2000 (type species)

Methanothermobacter crinale Cheng et al. 2012

Methanothermobacter defluvii (Kotelnikova et al. 1994) Boone 2002

Methanothermobacter marburgensis Wasserfallen et al. 2000

Methanothermobacter tenebrarum Nakamura et al. 2013

Methanothermobacter thermoflexus (Kotelnikova et al. 1994) Boone 2002

Methanothermobacter thermophilus (Laurinavichus et al. 1990) Boone 2002

Methanothermobacter wolfei corrig. (Winter et al. 1985) Wasserfallen et al. 2000

Family Methanothermaceae

Genus Methanothermus Stetter 1982

Methanothermus fervidus Stetter 1982 (type species)

Class Methanopyri

Order Methanopyrales

Family Methanopyraceae

Genus Methanopyrus Kurr et al. 1992

Methanopyrus kandleri Kurr et al. 1992 (type species)

Class Methanococci

Order Methanococcales

Family Methanococcaceae Balch and Wolfe 1981

Genus Methanococcus Kluyver and van Niel 1936

Methanococcus vannielii Stadtman and Barker 1951 (type species)

Methanococcus aeolicus

Methanococcus burtonii

Methanococcus chunghsingensis

Methanococcus deltae

Methanococcus jannaschii

Methanococcus maripaludis

Genus Methanofervidicoccus

Methanofervidicoccus abyssi Sakai et al. 2019 (type species)

Genus Methanothermococcus

Methanothermococcus thermolithotrophicus (Huber et al. 1984) Whitman 2002 (type species)

Family Methanocaldococcaceae

Genus Methanocaldococcus

Methanocaldococcus jannaschii (Jones et al. 1984) Whitman 2002 (type species)

Genus Methanotorris

Methanotorris igneus (Burggraf et al. 1990) Whitman 2002 (type species)

Phylum Thermoplasmatota

Class Thermoplasmata

Order Methanomassiliicoccales

Family Methanomassiliicoccaceae

Genus Methanomassiliicoccus Dridi et al. 2012

Methanomassiliicoccus luminyensis Dridi et al. 2012 (type species)

Family Methanomethylophilaceae

Genus Methanomethylophilus Borrel et al. 2024

Methanomethylophilus alvi Borrel et al. 2024 (type species)

See also

• Extremophile
• Hydrogen cycle
• Kraken Mare
• List of Archaea genera
• Methane clathrate
• Methanogens in digestive tract of ruminants
• Methanopyrus
• Methanotroph

References

1. Ernst, Leonard; Steinfeld, Benedikt; Barayeu, Uladzimir; Klintzsch, Thomas; Kurth, Markus; Grimm, Dirk; Dick, Tobias P.; Rebelein, Johannes G.; Bischofs, Ilka B.; Keppler, Frank (2022-03-17). "Methane formation driven by reactive oxygen species across all living organisms". Nature. 603 (7901): 482–487. Bibcode:2022Natur.603..482E. doi:10.1038/s41586-022-04511-9. ISSN 0028-0836. PMID 35264795.
2. Liu, Yuchen; Whitman, William B. (March 2008). "Metabolic, Phylogenetic, and Ecological Diversity of the Methanogenic Archaea". Annals of the New York Academy of Sciences. 1125 (1): 171–189. Bibcode:2008NYASA1125..171L. doi:10.1196/annals.1419.019. ISSN 0077-8923. PMID 18378594.
3. Peters, V.; Conrad, R. (1995). "Methanogenic and other strictly anaerobic bacteria in desert soil and other oxic sois". Applied and Environmental Microbiology. 61 (4): 1673–1676. Bibcode:1995ApEnM..61.1673P. doi:10.1128/AEM.61.4.1673-1676.1995. PMC 1388429. PMID 16535011.
4. "Archived copy". Archived from the original on 2009-03-27. Retrieved 2009-09-20.
5. Boone, David R. (2015). "Methanobacterium". Bergey's Manual of Systematics of Archaea and Bacteria. John Wiley & Sons, Ltd. pp. 1–8. doi:10.1002/9781118960608.gbm00495. ISBN 9781118960608.
6. Tung, H. C.; Bramall, N. E.; Price, P. B. (2005). "Microbial origin of excess methane in glacial ice and implications for life on Mars". Proceedings of the National Academy of Sciences. 102 (51): 18292–6. Bibcode:2005PNAS..10218292T. doi:10.1073/pnas.0507601102. PMC 1308353. PMID 16339015.
7. Icarus (vol. 178, p. 277)cs:Methanogen
8. Michał, Burdukiewicz; Gagat, Przemysław; Jabłoński, Sławomir; Chilimoniuk, Jarosław; Gaworski, Michał; Mackiewicz, Paweł; Marcin, Łukaszewicz (June 2018). "PhyMet 2 : a database and toolkit for phylogenetic and metabolic analyses of methanogens". Environmental Microbiology Reports. 10 (3): 378–382. Bibcode:2018EnvMR..10..378M. doi:10.1111/1758-2229.12648. ISSN 1758-2229. PMID 29624889.
9. "Leibniz Institute DSMZ: Welcome to the Leibniz Institute DSMZ". www.dsmz.de. Retrieved 2024-07-17.
10. Angel, Roey; Matthies, Diethart; Conrad, Ralf (2011-05-31). "Activation of Methanogenesis in Arid Biological Soil Crusts Despite the Presence of Oxygen". PLOS ONE. 6 (5): e20453. Bibcode:2011PLoSO...620453A. doi:10.1371/journal.pone.0020453. ISSN 1932-6203. PMC 3105065. PMID 21655270.
11. Angel, Roey; Claus, Peter; Conrad, Ralf (April 2012). "Methanogenic archaea are globally ubiquitous in aerated soils and become active under wet anoxic conditions". The ISME Journal. 6 (4): 847–862. Bibcode:2012ISMEJ...6..847A. doi:10.1038/ismej.2011.141. ISSN 1751-7362. PMC 3309352. PMID 22071343.
12. Conrad, Ralf (2020-06-11). "Methane Production in Soil Environments—Anaerobic Biogeochemistry and Microbial Life between Flooding and Desiccation". Microorganisms. 8 (6): 881. doi:10.3390/microorganisms8060881. ISSN 2076-2607. PMC 7357154. PMID 32545191.
13. Lyu, Zhe; Lu, Yahai (2017-11-14). "Metabolic shift at the class level sheds light on adaptation of methanogens to oxidative environments". The ISME Journal. 12 (2): 411–423. Bibcode:2018ISMEJ..12..411L. doi:10.1038/ismej.2017.173. ISSN 1751-7362. PMC 5776455. PMID 29135970.
14. Angle, Jordan C.; Morin, Timothy H.; Solden, Lindsey M.; Narrowe, Adrienne B.; Smith, Garrett J.; Borton, Mikayla A.; Rey-Sanchez, Camilo; Daly, Rebecca A.; Mirfenderesgi, Golnazalsdat; Hoyt, David W.; Riley, William J.; Miller, Christopher S.; Bohrer, Gil; Wrighton, Kelly C. (2017-11-16). "Methanogenesis in oxygenated soils is a substantial fraction of wetland methane emissions". Nature Communications. 8 (1): 1567. Bibcode:2017NatCo...8.1567A. doi:10.1038/s41467-017-01753-4. ISSN 2041-1723. PMC 5691036. PMID 29146959.
15. van Wolferen, Marleen; Pulschen, Andre Arashiro; Baum, Buzz; Gribaldo, Simonetta; Albers, Sonja-Verena (2022-10-17). "The cell biology of archaea". Nature Microbiology. 7 (11): 1744–1755. doi:10.1038/s41564-022-01215-8. ISSN 2058-5276. PMC 7613921. PMID 36253512.
16. Albers, Sonja-Verena; Meyer, Benjamin H. (June 2011). "The archaeal cell envelope". Nature Reviews Microbiology. 9 (6): 414–426. doi:10.1038/nrmicro2576. ISSN 1740-1526. PMID 21572458.
17. Thauer, Rudolf K.; Kaster, Anne-Kristin; Seedorf, Henning; Buckel, Wolfgang; Hedderich, Reiner (August 2008). "Methanogenic archaea: ecologically relevant differences in energy conservation". Nature Reviews Microbiology. 6 (8): 579–591. doi:10.1038/nrmicro1931. ISSN 1740-1526. PMID 18587410.
18. Chibani, Cynthia Maria; Mahnert, Alexander; Borrel, Guillaume; Almeida, Alexandre; Werner, Almut; Brugère, Jean-François; Gribaldo, Simonetta; Finn, Robert D.; Schmitz, Ruth A.; Moissl-Eichinger, Christine (2021-12-30). "A catalogue of 1,167 genomes from the human gut archaeome". Nature Microbiology. 7 (1): 48–61. doi:10.1038/s41564-021-01020-9. ISSN 2058-5276. PMC 8727293. PMID 34969981.
19. Protasov, Evgenii; Nonoh, James O.; Kästle Silva, Joana M.; Mies, Undine S.; Hervé, Vincent; Dietrich, Carsten; Lang, Kristina; Mikulski, Lena; Platt, Katja; Poehlein, Anja; Köhler-Ramm, Tim; Miambi, Edouard; Boga, Hamadi I.; Feldewert, Christopher; Ngugi, David K. (2023-11-15). "Diversity and taxonomic revision of methanogens and other archaea in the intestinal tract of terrestrial arthropods". Frontiers in Microbiology. 14. doi:10.3389/fmicb.2023.1281628. ISSN 1664-302X. PMC 10684969. PMID 38033561.
20. Thomas, Courtney M.; Desmond-Le Quéméner, Elie; Gribaldo, Simonetta; Borrel, Guillaume (2022-06-10). "Factors shaping the abundance and diversity of the gut archaeome across the animal kingdom". Nature Communications. 13 (1): 3358. Bibcode:2022NatCo..13.3358T. doi:10.1038/s41467-022-31038-4. ISSN 2041-1723. PMC 9187648. PMID 35688919.
21. Lyu, Zhe; Shao, Nana; Akinyemi, Taiwo; Whitman, William B. (July 2018). "Methanogenesis". Current Biology. 28 (13): R727–R732. Bibcode:2018CBio...28.R727L. doi:10.1016/j.cub.2018.05.021. PMID 29990451.
22. Kvenvolden, K. (1995). "A review of the geochemistry of methane in natural gas hydrate". Organic Geochemistry. 23 (11–12): 997–1008. Bibcode:1995OrGeo..23..997K. doi:10.1016/0146-6380(96)00002-2.
23. Milkov, Alexei V (2004). "Global estimates of hydrate-bound gas in marine sediments: how much is really out there?". Earth-Science Reviews. 66 (3–4): 183–197. Bibcode:2004ESRv...66..183M. doi:10.1016/j.earscirev.2003.11.002.
24. "Crater Critters: Where Mars Microbes Might Lurk". Space.com. 20 December 2005. Retrieved 16 December 2014.
25. "NASA Rover on Mars Detects Puff of Gas That Hints at Possibility of Life". The New York Times. 22 June 2019.
26. Thauer, R. K. & Shima, S. (2006). "Biogeochemistry: Methane and microbes". Nature. 440 (7086): 878–879. Bibcode:2006Natur.440..878T. doi:10.1038/440878a. PMID 16612369. S2CID 4373591.
27. Youngblut, Nicholas D.; Reischer, Georg H.; Dauser, Silke; Maisch, Sophie; Walzer, Chris; Stalder, Gabrielle; Farnleitner, Andreas H.; Ley, Ruth E. (2021-10-26). "Vertebrate host phylogeny influences gut archaeal diversity". Nature Microbiology. 6 (11): 1443–1454. doi:10.1038/s41564-021-00980-2. ISSN 2058-5276. PMC 8556154. PMID 34702978.
28. Thomas, Courtney M.; Desmond-Le Quéméner, Elie; Gribaldo, Simonetta; Borrel, Guillaume (2022-06-10). "Factors shaping the abundance and diversity of the gut archaeome across the animal kingdom". Nature Communications. 13 (1): 3358. Bibcode:2022NatCo..13.3358T. doi:10.1038/s41467-022-31038-4. ISSN 2041-1723. PMC 9187648. PMID 35688919.
29. Protasov, Evgenii; Nonoh, James O.; Kästle Silva, Joana M.; Mies, Undine S.; Hervé, Vincent; Dietrich, Carsten; Lang, Kristina; Mikulski, Lena; Platt, Katja; Poehlein, Anja; Köhler-Ramm, Tim; Miambi, Edouard; Boga, Hamadi I.; Feldewert, Christopher; Ngugi, David K. (2023-11-15). "Diversity and taxonomic revision of methanogens and other archaea in the intestinal tract of terrestrial arthropods". Frontiers in Microbiology. 14. doi:10.3389/fmicb.2023.1281628. ISSN 1664-302X. PMC 10684969. PMID 38033561.
30. Gao, Beile; Gupta, Radhey S (2007). "Phylogenomic analysis of proteins that are distinctive of Archaea and its main subgroups and the origin of methanogenesis". BMC Genomics. 8 (1): 86. doi:10.1186/1471-2164-8-86. PMC 1852104. PMID 17394648.
31. Rauch, Benjamin Julius; Gustafson, Andrew; Perona, John J. (December 2014). "Novel proteins for homocysteine biosynthesis in anaerobic microorganisms". Molecular Microbiology. 94 (6): 1330–1342. doi:10.1111/mmi.12832. ISSN 0950-382X. PMID 25315403.
32. Chen, Sheng-Chung; Weng, Chieh-Yin; Lai, Mei-Chin; Tamaki, Hideyuki; Narihiro, Takashi (October 2019). "Comparative genomic analyses reveal trehalose synthase genes as the signature in genus Methanoculleus". Marine Genomics. 47: 100673. Bibcode:2019MarGn..4700673C. doi:10.1016/j.margen.2019.03.008. PMID 30935830. S2CID 91188321.
33. Guan, Yue; Ngugi, David K.; Vinu, Manikandan; Blom, Jochen; Alam, Intikhab; Guillot, Sylvain; Ferry, James G.; Stingl, Ulrich (2019-04-24). "Comparative Genomics of the Genus Methanohalophilus, Including a Newly Isolated Strain From Kebrit Deep in the Red Sea". Frontiers in Microbiology. 10: 839. doi:10.3389/fmicb.2019.00839. ISSN 1664-302X. PMC 6491703. PMID 31068917.
34. Borton, Mikayla A.; Daly, Rebecca A.; O'Banion, Bridget; Hoyt, David W.; Marcus, Daniel N.; Welch, Susan; Hastings, Sybille S.; Meulia, Tea; Wolfe, Richard A.; Booker, Anne E.; Sharma, Shikha (December 2018). "Comparative genomics and physiology of the genus Methanohalophilus, a prevalent methanogen in hydraulically fractured shale". Environmental Microbiology. 20 (12): 4596–4611. Bibcode:2018EnvMi..20.4596B. doi:10.1111/1462-2920.14467. ISSN 1462-2912. PMID 30394652. S2CID 53220420.
35. Söllinger, Andrea; Schwab, Clarissa; Weinmaier, Thomas; Loy, Alexander; Tveit, Alexander T.; Schleper, Christa; Urich, Tim (January 2016). King, Gary (ed.). "Phylogenetic and genomic analysis of Methanomassiliicoccales in wetlands and animal intestinal tracts reveals clade-specific habitat preferences". FEMS Microbiology Ecology. 92 (1): fiv149. doi:10.1093/femsec/fiv149. hdl:10037/8522. ISSN 1574-6941. PMID 26613748.
36. Lyu, Zhe; Lu, Yahai (June 2015). "Comparative genomics of three M ethanocellales strains reveal novel taxonomic and metabolic features: Comparative genomics of three Methanocellales strains". Environmental Microbiology Reports. 7 (3): 526–537. doi:10.1111/1758-2229.12283. PMID 25727385.
37. Lyu, Zhe; Lu, Yahai (February 2018). "Metabolic shift at the class level sheds light on adaptation of methanogens to oxidative environments". The ISME Journal. 12 (2): 411–423. Bibcode:2018ISMEJ..12..411L. doi:10.1038/ismej.2017.173. ISSN 1751-7362. PMC 5776455. PMID 29135970.
38. Borrel, Guillaume; Parisot, Nicolas; Harris, Hugh MB; Peyretaillade, Eric; Gaci, Nadia; Tottey, William; Bardot, Olivier; Raymann, Kasie; Gribaldo, Simonetta; Peyret, Pierre; O’Toole, Paul W (2014). "Comparative genomics highlights the unique biology of Methanomassiliicoccales, a Thermoplasmatales-related seventh order of methanogenic archaea that encodes pyrrolysine". BMC Genomics. 15 (1): 679. doi:10.1186/1471-2164-15-679. ISSN 1471-2164. PMC 4153887. PMID 25124552.
39. Borrel, Guillaume; O’Toole, Paul W.; Harris, Hugh M.B.; Peyret, Pierre; Brugère, Jean-François; Gribaldo, Simonetta (October 2013). "Phylogenomic Data Support a Seventh Order of Methylotrophic Methanogens and Provide Insights into the Evolution of Methanogenesis". Genome Biology and Evolution. 5 (10): 1769–1780. doi:10.1093/gbe/evt128. ISSN 1759-6653. PMC 3814188. PMID 23985970.
40. Blaut, M. (1994). "Metabolism of methanogens". Antonie van Leeuwenhoek. 66 (1–3): 187–208. doi:10.1007/bf00871639. ISSN 0003-6072. PMID 7747931. S2CID 23706408.
41. Dybas, M; Konisky, J (1992). "Energy transduction in the methanogen Methanococcus voltae is based on a sodium current". J Bacteriol. 174 (17): 5575–5583. doi:10.1128/jb.174.17.5575-5583.1992. PMC 206501. PMID 1324904.
42. Karrasch, M.; Börner, G.; Enssle, M.; Thauer, R. K. (1990-12-12). "The molybdoenzyme formylmethanofuran dehydrogenase from Methanosarcina barkeri contains a pterin cofactor". European Journal of Biochemistry. 194 (2): 367–372. doi:10.1111/j.1432-1033.1990.tb15627.x. ISSN 0014-2956. PMID 2125267.
43. Börner, G.; Karrasch, M.; Thauer, R. K. (1991-09-23). "Molybdopterin adenine dinucleotide and molybdopterin hypoxanthine dinucleotide in formylmethanofuran dehydrogenase from Methanobacterium thermoautotrophicum (Marburg)". FEBS Letters. 290 (1–2): 31–34. Bibcode:1991FEBSL.290...31B. doi:10.1016/0014-5793(91)81218-w. ISSN 0014-5793. PMID 1915887. S2CID 24174561.
44. Schmitz, Ruth A.; Albracht, Simon P. J.; Thauer, Rudolf K. (1992-11-01). "A molybdenum and a tungsten isoenzyme of formylmethanofuran dehydrogenase in the thermophilic archaeon Methanobacterium wolfei". European Journal of Biochemistry. 209 (3): 1013–1018. doi:10.1111/j.1432-1033.1992.tb17376.x. ISSN 1432-1033. PMID 1330558.
45. Zirngibl, C (February 1990). "N5,N10-Methylenetetrahydromethanopterin dehydrogenase from Methanobacterium thermoautotrophicum has hydrogenase activity". Laboratorium Fir Mikrobiologie. 261 (1): 112–116. Bibcode:1990FEBSL.261..112Z. doi:10.1016/0014-5793(90)80649-4.
46. te Brömmelstroet, B. W.; Geerts, W. J.; Keltjens, J. T.; van der Drift, C.; Vogels, G. D. (1991-09-20). "Purification and properties of 5,10-methylenetetrahydromethanopterin dehydrogenase and 5,10-methylenetetrahydromethanopterin reductase, two coenzyme F420-dependent enzymes, from Methanosarcina barkeri". Biochimica et Biophysica Acta (BBA) - Protein Structure and Molecular Enzymology. 1079 (3): 293–302. doi:10.1016/0167-4838(91)90072-8. ISSN 0006-3002. PMID 1911853.
47. Kengen, Servé W. M.; Mosterd, Judith J.; Nelissen, Rob L. H.; Keltjens, Jan T.; Drift, Chris van der; Vogels, Godfried D. (1988-08-01). "Reductive activation of the methyl-tetrahydromethanopterin: coenzyme M methyltransferase from Methanobacterium thermoautotrophicum strain ΔH". Archives of Microbiology. 150 (4): 405–412. Bibcode:1988ArMic.150..405K. doi:10.1007/BF00408315. ISSN 0302-8933. S2CID 36366503.
48. Bobik, T. A.; Olson, K. D.; Noll, K. M.; Wolfe, R. S. (1987-12-16). "Evidence that the heterodisulfide of coenzyme M and 7-mercaptoheptanoylthreonine phosphate is a product of the methylreductase reaction in Methanobacterium". Biochemical and Biophysical Research Communications. 149 (2): 455–460. doi:10.1016/0006-291x(87)90389-5. ISSN 0006-291X. PMID 3122735.
49. Ellermann, J.; Hedderich, R.; Böcher, R.; Thauer, R. K. (1988-03-15). "The final step in methane formation. Investigations with highly purified methyl-CoM reductase (component C) from Methanobacterium thermoautotrophicum (strain Marburg)". European Journal of Biochemistry. 172 (3): 669–677. doi:10.1111/j.1432-1033.1988.tb13941.x. ISSN 0014-2956. PMID 3350018.
50. Appels, Lise; et al. (2008). "Principles and potential of the anaerobic digestion of waste-activated sludge" Progress in Energy and Combustion Science. 34 (6): 755 -781. doi: 10.1016/j.pecs.2008.06.002
51. Christensen, Thomas H; et al. (2010). "Anaerobic Digestion: Process" Solid Waste Technology & Management, Volume 1 & 2. doi: 10.1002/9780470666883.ch372
52. Shah, Fayyaz Ali, et al. (2014). “Microbial Ecology of Anaerobic Digesters: The Key Players of Anaerobiosis” ScientificWorldJournal. 3852369 (1). doi:10.1155/2014/183752
53. Lettinga, G (1995). "Anaerobic Digestion and Wastewater Treatment Systems". Antonie van Leeuwenhoek. 67 (1): 3–28. doi:10.1007/bf00872193. PMID 7741528. S2CID 9415571.
54. Tabatabaei, Meisa; et al. (2010). "Importance of the methanogenic archaea populations in anaerobic wastewater treatments" (PDF). Process Biochemistry. 45 (8): 1214–1225. doi:10.1016/j.procbio.2010.05.017.
55. Marihiro, Takashi., Sekiguchi, Yuji. (2007). "Microbial communities in anaerobic digestion processes for waste and wastewater treatment: a microbiological update" Current Opinion in Biotechnology. 18 (3): 273-278. doi: 10.1016/j.copbio.2007.04.003
56. "Advanced anaerobic wastewater treatment in the near future". Water Science and Technology. 35 (10). 1997. doi:10.1016/S0273-1223(97)00222-9.
57. Woese, Carl R.; Fox, George E. (November 1977). "Phylogenetic structure of the prokaryotic domain: The primary kingdoms". Proceedings of the National Academy of Sciences. 74 (11): 5088–5090. Bibcode:1977PNAS...74.5088W. doi:10.1073/pnas.74.11.5088. ISSN 0027-8424. PMC 432104. PMID 270744.
58. Evans, Paul N.; Parks, Donovan H.; Chadwick, Grayson L.; Robbins, Steven J.; Orphan, Victoria J.; Golding, Suzanne D.; Tyson, Gene W. (2015-10-23). "Methane metabolism in the archaeal phylum Bathyarchaeota revealed by genome-centric metagenomics". Science. 350 (6259): 434–438. Bibcode:2015Sci...350..434E. doi:10.1126/science.aac7745. ISSN 0036-8075. PMID 26494757.
59. Qi, Yan-Ling; Evans, Paul N.; Li, Yu-Xian; Rao, Yang-Zhi; Qu, Yan-Ni; Tan, Sha; Jiao, Jian-Yu; Chen, Ya-Ting; Hedlund, Brian P.; Shu, Wen-Sheng; Hua, Zheng-Shuang; Li, Wen-Jun (2021-08-31). "Comparative Genomics Reveals Thermal Adaptation and a High Metabolic Diversity in Candidatus Bathyarchaeia"". mSystems. 6 (4): e0025221. doi:10.1128/msystems.00252-21. ISSN 2379-5077. PMC 8407382. PMID 34282939.
60. Khomyakova, Maria A.; Merkel, Alexander Y.; Mamiy, Dana D.; Klyukina, Alexandra A.; Slobodkin, Alexander I. (2023-08-22). "Phenotypic and genomic characterization of Bathyarchaeum tardum gen. nov., sp. nov., a cultivated representative of the archaeal class Bathyarchaeia". Frontiers in Microbiology. 14. doi:10.3389/fmicb.2023.1214631. ISSN 1664-302X. PMC 10477458. PMID 37675420.
61. Zhou, Zhichao; Pan, Jie; Wang, Fengping; Gu, Ji-Dong; Li, Meng (2018-09-01). "Bathyarchaeota: globally distributed metabolic generalists in anoxic environments". FEMS Microbiology Reviews. 42 (5): 639–655. doi:10.1093/femsre/fuy023. ISSN 1574-6976. PMID 29790926.
62. Yu, Tiantian; Wu, Weichao; Liang, Wenyue; Lever, Mark Alexander; Hinrichs, Kai-Uwe; Wang, Fengping (2018-06-05). "Growth of sedimentary Bathyarchaeota on lignin as an energy source". Proceedings of the National Academy of Sciences. 115 (23): 6022–6027. Bibcode:2018PNAS..115.6022Y. doi:10.1073/pnas.1718854115. ISSN 0027-8424. PMC 6003339. PMID 29773709.
63. Yu, Tiantian; Hu, Haining; Zeng, Xianhong; Wang, Yinzhao; Pan, Donald; Deng, Longhui; Liang, Lewen; Hou, Jialin; Wang, Fengping (September 2023). "Widespread Bathyarchaeia encode a novel methyltransferase utilizing lignin-derived aromatics". mLife. 2 (3): 272–282. doi:10.1002/mlf2.12082. ISSN 2097-1699. PMC 10989822. PMID 38817817.
64. Paul, Kristina; Nonoh, James O.; Mikulski, Lena; Brune, Andreas (December 2012). ""Methanoplasmatales," Thermoplasmatales-Related Archaea in Termite Guts and Other Environments, Are the Seventh Order of Methanogens". Applied and Environmental Microbiology. 78 (23): 8245–8253. Bibcode:2012ApEnM..78.8245P. doi:10.1128/aem.02193-12. ISSN 0099-2240. PMC 3497382. PMID 23001661.
65. Dridi, Bédis; Fardeau, Marie-Laure; Ollivier, Bernard; Raoult, Didier; Drancourt, Michel (2012-08-01). "Methanomassiliicoccus luminyensis gen. nov., sp. nov., a methanogenic archaeon isolated from human faeces". International Journal of Systematic and Evolutionary Microbiology. 62 (Pt_8): 1902–1907. doi:10.1099/ijs.0.033712-0. ISSN 1466-5026. PMID 22859731.
66. Iino, Takao; Tamaki, Hideyuki; Tamazawa, Satoshi; Ueno, Yoshiyuki; Ohkuma, Moriya; Suzuki, Ken-ichiro; Igarashi, Yasuo; Haruta, Shin (2013). "Candidatus Methanogranum caenicola: a Novel Methanogen from the Anaerobic Digested Sludge, and Proposal of Methanomassiliicoccaceae fam. nov. and Methanomassiliicoccales ord. nov., for a Methanogenic Lineage of the Class Thermoplasmata". Microbes and Environments. 28 (2): 244–250. doi:10.1264/jsme2.ME12189. ISSN 1342-6311. PMC 4070666. PMID 23524372.
67. Sorokin, Dimitry Y.; Merkel, Alexander Y.; Abbas, Ben; Makarova, Kira S.; Rijpstra, W. Irene C.; Koenen, M.; Sinninghe Damsté, Jaap S.; Galinski, Erwin A.; Koonin, Eugene V.; van Loosdrecht, Mark C. M. (2018-07-01). "Methanonatronarchaeum thermophilum gen. nov., sp. nov. and 'Candidatus Methanohalarchaeum thermophilum', extremely halo(natrono)philic methyl-reducing methanogens from hypersaline lakes comprising a new euryarchaeal class Methanonatronarchaeia classis nov". International Journal of Systematic and Evolutionary Microbiology. 68 (7): 2199–2208. doi:10.1099/ijsem.0.002810. ISSN 1466-5026. PMC 6978985. PMID 29781801.
68. Sorokin, Dimitry Y.; Makarova, Kira S.; Abbas, Ben; Ferrer, Manuel; Golyshin, Peter N.; Galinski, Erwin A.; Ciordia, Sergio; Mena, María Carmen; Merkel, Alexander Y.; Wolf, Yuri I.; van Loosdrecht, Mark C. M.; Koonin, Eugene V. (2017-05-30). "Discovery of extremely halophilic, methyl-reducing euryarchaea provides insights into the evolutionary origin of methanogenesis". Nature Microbiology. 2 (8): 17081. doi:10.1038/nmicrobiol.2017.81. ISSN 2058-5276. PMC 5494993. PMID 28555626.
69. Sorokin, Dimitry Y.; Merkel, Alexander Y.; Abbas, Ben (November 2022). "Ecology of Methanonatronarchaeia". Environmental Microbiology. 24 (11): 5217–5229. Bibcode:2022EnvMi..24.5217S. doi:10.1111/1462-2920.16108. ISSN 1462-2912. PMC 9796771. PMID 35726892.
70. Steiniger, Fabian; Sorokin, Dimitry Y.; Deppenmeier, Uwe (January 2022). "Process of energy conservation in the extremely haloalkaliphilic methyl-reducing methanogen Methanonatronarchaeum thermophilum". The FEBS Journal. 289 (2): 549–563. doi:10.1111/febs.16165. ISSN 1742-464X. PMID 34435454.
71. Mei, Ran; Kaneko, Masanori; Imachi, Hiroyuki; Nobu, Masaru K (2023-02-03). Ma, Li-Jun (ed.). "The origin and evolution of methanogenesis and Archaea are intertwined". PNAS Nexus. 2 (2): pgad023. doi:10.1093/pnasnexus/pgad023. ISSN 2752-6542. PMC 9982363. PMID 36874274.
72. Oren, Aharon; Arahal, David R.; Göker, Markus; Moore, Edward R. B.; Rossello-Mora, Ramon; Sutcliffe, Iain C. (2023-05-01). "International Code of Nomenclature of Prokaryotes. Prokaryotic Code (2022 Revision)". International Journal of Systematic and Evolutionary Microbiology. 73 (5a). doi:10.1099/ijsem.0.005585. hdl:10261/338243. ISSN 1466-5026. PMID 37219928.
73. "Phylum: Methanobacteriota". lpsn.dsmz.de. Retrieved 2024-07-16.
74. Göker, Markus; Oren, Aharon (2024-01-22). "Valid publication of names of two domains and seven kingdoms of prokaryotes". International Journal of Systematic and Evolutionary Microbiology. 74 (1). doi:10.1099/ijsem.0.006242. ISSN 1466-5026. PMID 38252124.
75. "Leibniz Institute DSMZ: Welcome to the Leibniz Institute DSMZ". www.dsmz.de. Retrieved 2024-07-16.