Methanothrix Explained

In the taxonomy of microorganisms, the Methanothrix is a genus of methanogenic archaea within the Euryarchaeota.[1] [2] Methanothrix cells were first isolated from a mesophilic sewage digester but have since been found in many anaerobic and aerobic environments.[3] [4] Methanothrix were originally understood to be obligate anaerobes that can survive exposure to high concentrations of oxygen,[5] [6] but recent studies have shown at least one Candidatus operational taxonomic unit proposed to be in the Methanothrix genus not only survives but remains active in oxic soils. This proposed species, Ca. Methanothrix paradoxum, is frequently found in methane-releasing ecosystems and is the dominant methanogen in oxic soils.

Methanothrix are non-motile rod-shaped cells which connect together to form long filaments.[7] These filaments are enclosed in a proteinaceous sheath. Methanothrix species, like their close relative Methanosarcina barkeri, have membranes entirely composed of diphytanylglycerol diethers.[8] [9]

Metabolism

Methanothrix species use acetate[16] [17] and carbon dioxide[18] as carbon substrates.

When using acetate, Methanothrix species use an incomplete citric acid cycle in the oxidative direction. After formation of acetyl-CoA, the carbon-carbon bond of acetate is cleaved by a carbon monoxide dehydrogenase/acetyl-CoA synthase enzyme. The methyl moiety is transferred through multiple complexes until it is finally reduced to methane by a methyl-CoM reductase.

Methanothrix species have been observed receiving electrons to reduce carbon dioxide to methane through direct interspecies electron transfer (DIET) with Geobacter species.[19] Geobacter sulfurreducens transfers electrons into Methanothrix cells using electrically conductive pili.[20]

Microbial Ecology

Compared to the acetotrophic Methanosarcina species, Methanothrix species have lower Monod Equation parameters. Methanothrix have slower maximum growth rates and smaller half-saturation coefficients due to differences in the genera's aceticlastic pathways.[21] Consequently, when acetate concentrations are high, Methanothrix species are likely to be outcompeted by Methanosarcina, which can utilize the available substrate faster. However, in low acetate environments, Methanothrix species will dominate due to their lower minimum threshold for acetate. This expectation is consistent with observations of abundant Methanothrix in low-acetate ecosystems across the world.[22] [23]

Because Methanothrix species are well adapted to survive exposure to oxygen and thrive using either acetate or carbon dioxide as a carbon substrate, they are thought to be one of the largest microbial contributors to methanogenesis on Earth.[24]

See also

Notes and References

  1. See the NCBI webpage on Methanothrix. Data extracted from the Web site: NCBI taxonomy resources. National Center for Biotechnology Information. 2007-03-19.
  2. Web site: J.P. Euzéby . Methanothrix . 2021-11-17 . List of Prokaryotic names with Standing in Nomenclature (LPSN).
  3. Holmes . Dawn E. . Shrestha . Pravin M. . Walker . David J. F. . Dang . Yan . Nevin . Kelly P. . Woodard . Trevor L. . Lovley . Derek R. . 2017 . Schloss . Patrick D. . Metatranscriptomic Evidence for Direct Interspecies Electron Transfer between Geobacter and Methanothrix Species in Methanogenic Rice Paddy Soils . Applied and Environmental Microbiology . en . 83 . 9 . 10.1128/AEM.00223-17 . 0099-2240 . 5394310 . 28258137.
  4. 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 . en . 8 . 1 . 1567 . 10.1038/s41467-017-01753-4 . 2041-1723 . 5691036 . 29146959.
  5. Huser . Beat A. . Wuhrmann . Karl . Zehnder . Alexander J. B. . 1982-07-01 . Methanothrix soehngenii gen. nov. sp. nov., a new acetotrophic non-hydrogen-oxidizing methane bacterium . Archives of Microbiology . en . 132 . 1 . 1–9 . 10.1007/BF00690808 . 1432-072X.
  6. PATEL . GIRISHCHANDRA B. . SPROTT . G. DENNIS . 1990 . Methanosaeta concilii gen. nov., sp. nov. ("Methanothrix concilii") and Methanosaeta thermoacetophila nom. rev., comb. nov.† . International Journal of Systematic and Evolutionary Microbiology . 40 . 1 . 79–82 . 10.1099/00207713-40-1-79 . 1466-5034.
  7. Koga . Y . Nishihara . M . Morii . H . Akagawa-Matsushita . M . 1993 . Ether polar lipids of methanogenic bacteria: structures, comparative aspects, and biosyntheses . Microbiological Reviews . en . 57 . 1 . 164–182 . 10.1128/mr.57.1.164-182.1993 . 0146-0749 . 372904 . 8464404.
  8. Ekiel . I . Sprott . G D . Patel . G B . 1985 . Acetate and CO2 assimilation by Methanothrix concilii . Journal of Bacteriology . en . 162 . 3 . 905–908 . 10.1128/jb.162.3.905-908.1985 . 0021-9193 . 215861 . 3922956.
  9. Langworthy . T. A. . Tornabene . T. G. . Holzer . G. . 1982-05-01 . Lipids of Archaebacteria . Zentralblatt für Bakteriologie Mikrobiologie und Hygiene: I. Abt. Originale C: Allgemeine, angewandte und ökologische Mikrobiologie . 3 . 2 . 228–244 . 10.1016/S0721-9571(82)80036-7 . 0721-9571.
  10. Web site: The LTP . 10 May 2023.
  11. Web site: LTP_all tree in newick format. 10 May 2023.
  12. Web site: LTP_06_2022 Release Notes. 10 May 2023.
  13. Web site: GTDB release 08-RS214 . Genome Taxonomy Database. 10 May 2023.
  14. Web site: ar53_r214.sp_label . Genome Taxonomy Database. 10 May 2023.
  15. Web site: Taxon History . Genome Taxonomy Database. 10 May 2023.
  16. Jetten . M . 1992 . Methanogenesis from acetate: a comparison of the acetate metabolism in Methanothrix soehngenii and Methanosarcina spp. . FEMS Microbiology Letters . 88 . 3–4 . 181–197 . 10.1016/0378-1097(92)90802-u . 0378-1097.
  17. Welte . Cornelia . Deppenmeier . Uwe . 2014-07-01 . Bioenergetics and anaerobic respiratory chains of aceticlastic methanogens . Biochimica et Biophysica Acta (BBA) - Bioenergetics . 18th European Bioenergetics Conference 2014 Lisbon, Portugal . 1837 . 7 . 1130–1147 . 10.1016/j.bbabio.2013.12.002 . 24333786 . 0005-2728. 2066/189998 . free .
  18. Rotaru . Amelia-Elena . Shrestha . Pravin Malla . Liu . Fanghua . Shrestha . Minita . Shrestha . Devesh . Embree . Mallory . Zengler . Karsten . Wardman . Colin . Nevin . Kelly P. . Lovley . Derek R. . 2013-12-13 . A new model for electron flow during anaerobic digestion: direct interspecies electron transfer to Methanosaeta for the reduction of carbon dioxide to methane . Energy & Environmental Science . en . 7 . 1 . 408–415 . 10.1039/C3EE42189A . 1754-5706.
  19. Lovley . Derek R. . 2017-09-08 . Syntrophy Goes Electric: Direct Interspecies Electron Transfer . Annual Review of Microbiology . en . 71 . 1 . 643–664 . 10.1146/annurev-micro-030117-020420 . 28697668 . 0066-4227.
  20. Malvankar . Nikhil S . Lovley . Derek R . 2014-06-01 . Microbial nanowires for bioenergy applications . Current Opinion in Biotechnology . Energy biotechnology • Environmental biotechnology . 27 . 88–95 . 10.1016/j.copbio.2013.12.003 . 24863901 . 0958-1669.
  21. Conklin . Anne . Stensel . H. David . Ferguson . John . 2006 . Growth Kinetics and Competition Between Methanosarcina and Methanosaeta in Mesophilic Anaerobic Digestion . Water Environment Research . en . 78 . 5 . 486–496 . 10.2175/106143006X95393 . 16752610 . 1061-4303.
  22. Fey . Axel . Conrad . Ralf . 2000 . Effect of Temperature on Carbon and Electron Flow and on the Archaeal Community in Methanogenic Rice Field Soil . Applied and Environmental Microbiology . en . 66 . 11 . 4790–4797 . 10.1128/AEM.66.11.4790-4797.2000 . 0099-2240 . 92381 . 11055925.
  23. Griffin . M. E. . McMahon . K. D. . Mackie . R. I. . Raskin . L. . 1998-02-05 . Methanogenic population dynamics during start-up of anaerobic digesters treating municipal solid waste and biosolids . Biotechnology and Bioengineering . 57 . 3 . 342–355 . 10.1002/(sici)1097-0290(19980205)57:3<342::aid-bit11>3.0.co;2-i . 0006-3592 . 10099211.
  24. Smith . Kerry S. . Ingram-Smith . Cheryl . 2007 . Methanosaeta, the forgotten methanogen? . Trends in Microbiology . 15 . 4 . 150–155 . 10.1016/j.tim.2007.02.002 . 17320399 . 0966-842X.

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