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Chemotroph

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A chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments.[1] These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototrophs, which use photons. Chemotrophs can be either autotrophic or heterotrophic. Chemotrophs can be found in areas where electron donors are present in high concentration, for instance around hydrothermal vents.[2] Some examples of chemotrophic organisms include iron-oxidizing bacteria and methanogenic archaea.

Chemoautotroph

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A black smoker vent in the Atlantic Ocean, providing energy and nutrients for chemotrophs

Chemoautotrophs are autotrophic organisms that can rely on chemosynthesis, i.e. deriving biological energy from chemical reactions of environmental inorganic substrates and synthesizing all necessary organic compounds from carbon dioxide. Chemoautotrophs can use inorganic energy sources such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia or organic sources to produce energy. Most chemoautotrophs are prokaryotic extremophiles, bacteria, or archaea that live in otherwise hostile environments (such as deep sea vents) and are the primary producers in such ecosystems. Chemoautotrophs generally fall into several groups: methanogens, sulfur oxidizers and reducers, nitrifiers, anammox bacteria, and thermoacidophiles. An example of one of these prokaryotes would be Sulfolobus. Chemolithotrophic growth can be very fast, such as Hydrogenovibrio crunogenus with a doubling time around one hour.[3][4]

The term "chemosynthesis", coined in 1897 by Wilhelm Pfeffer, originally was defined as the energy production by oxidation of inorganic substances in association with autotrophy — what would be named today as chemolithoautotrophy. Later, the term would include also the chemoorganoautotrophy, that is, it can be seen as a synonym of chemoautotrophy.[5][6]

Chemoheterotroph

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Chemoheterotrophs (or chemotrophic heterotrophs) are unable to fix carbon to form their own organic compounds. Chemoheterotrophs can be chemolithoheterotrophs, utilizing inorganic electron sources such as sulfur, iron, or, much more commonly, chemoorganoheterotrophs, utilizing organic electron sources such as carbohydrates, lipids, and proteins.[7][8][9][10] Most animals and fungi are examples of chemoheterotrophs, as are some halophiles.[11][12]

Iron-oxidizing bacteria

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Iron-oxidizing bacteria are chemotrophic bacteria that derive energy by oxidizing dissolved ferrous iron. They are known to grow and proliferate in waters containing iron concentrations as low as 0.1 mg/L. However, at least 0.3 ppm of dissolved oxygen is needed to carry out the oxidation.[13]

Iron has many existing roles in biology not related to redox reactions; examples include iron–sulfur proteins, hemoglobin, and coordination complexes. Iron has a widespread distribution globally and is considered one of the most abundant in the Earth's crust, soil, and sediments.[14] Iron is a trace element in marine environments.[14] Its role as the electron donor for some chemolithotrophs is probably very ancient.[15]

Methanogens

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Methanogens are chemotrophic archaea that obtain energy most commonly through CO2 reduction by H2 (hydrogenotrophs) or fermentation of acetate (acetoclastic).[16] They are distinct from other bacteria or archea that do not depend on methane synthesis for energy but produce methane as a byproduct of their other metabolic processes.[17] Methanogens are also different from bacteria and eukarya due to a lack of peptidoglycan in their cell wall, rather methanogens contain either pseudomurein, heteropolysaccharide, or protein-based cell walls.[18] Species that reduce CO2 are chemoautotrophs and fix inorganic carbon, however, a few species use organic carbon in the form of acetate, making them chemoheterotrophs.[19] Methanogens belong to the Methanobacteriota kingdom.[20] Methanogens are a part of an ancient monophyletic lineage, the Methanobacteriati phylum (formerly "Euryarcheota"), and can be classified into three classes, six orders, twelve families and thirty-five genera.[21][22] Methanogenic metabolic pathways are thought to be present in some of the earliest organisms that occupied the earth.[23][24] Today, methanogens can be found in a wide range of environments, both oxic and anoxic and both terrestrial and aquatic, especially environments containing low sulfate.[25][17] Their activity is strongly regulated by temperature, pH, substrate and nutrient availability, as well as competition with other anaerobic microbes, all of which influence their distribution across diverse environments.[26][27]

Methanogenic archaea are involved in the late steps of degradation of organic matter.[25][28] In many anaerobic environments, methanogens form syntropic relationships with other fermentative bacteria that supply them with substrates such as H2, formate, and acetate.[29] Since the energy yield of methanogenesis is relatively low compared to other processes, methanogenesis does not become the dominant process until the more energy-rich electron acceptors such as O2, NO3-, and SO42- have already been depleted.[30] Due to the absence of these electron acceptors, methanogens can then catalyze the final step of the degradation of organic matter which is essential for anaerobic environments.[31] While different organisms may use different substrates, they all share methane as the final metabolic product, and they are all anaerobic.[25] In addition to CO2 and acetate, methanogens also use formate, methylamine and other small molecules to produce CH4.[32] Regardless of the substrate, all methanogenic archaea utilize the enzyme methyl-coenzyme M reductase, which performs the final step of reducing methyl-coenzyme M to methane.[20][28] Methanogens also possess several unique coenzymes such as coenzyme F430 and methanopterin, among others.[33] Methanogenic activity contributes to methane that is locked in long-term reservoirs such as permafrost, and as climate warming accelerates thawing of frozen soils, methane production by methanogens is expected increase.[34][35] As methane has around 25-30 times the global warming potential of CO2, methane is one of the greenhouse gases driving climate change that is a source of concern for climate scientists.[36]

See also

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Notes

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  1. ↑ Chang, Kenneth (12 September 2016). "Visions of Life on Mars in Earth's Depths". The New York Times. Retrieved 12 September 2016.
  2. ↑ Zeng, Xiang; Alain, Karine; Shao, Zongze (January 2021). "Microorganisms from deep-sea hydrothermal vents". Marine Life Science & Technology. 3 (2): 204–230. Bibcode:2021MLST....3..204Z. doi:10.1007/s42995-020-00086-4. ISSN 2662-1746. PMC 10077256. PMID 37073341.
  3. ↑ Dobrinski, K. P. (2005). "The Carbon-Concentrating Mechanism of the Hydrothermal Vent Chemolithoautotroph Thiomicrospira crunogena". Journal of Bacteriology. 187 (16): 5761–5766. Bibcode:2005JBact.187.5761D. doi:10.1128/JB.187.16.5761-5766.2005. PMC 1196061. PMID 16077123.
  4. ↑ Rich Boden; Kathleen M. Scott; J. Williams; S. Russel; K. Antonen; Alexander W. Rae; Lee P. Hutt (June 2017). "An evaluation of Thiomicrospira, Hydrogenovibrio and Thioalkalimicrobium: reclassification of four species of Thiomicrospira to each Thiomicrorhabdus gen. nov. and Hydrogenovibrio, and reclassification of all four species of Thioalkalimicrobium to Thiomicrospira". International Journal of Systematic and Evolutionary Microbiology. 67 (5): 1140–1151. Bibcode:2017IJSEM..67.1140B. doi:10.1099/ijsem.0.001855. hdl:10026.1/8374. PMID 28581925.
  5. ↑ Kelly, D. P.; Wood, A. P. (2006). "The Chemolithotrophic Prokaryotes". The Prokaryotes. New York: Springer. pp. 441–456. doi:10.1007/0-387-30742-7_15. ISBN 978-0-387-25492-0.
  6. ↑ Schlegel, H. G. (1975). "Mechanisms of Chemo-Autotrophy" (PDF). In Kinne, O. (ed.). Marine Ecology. Vol. 2, Part I. Wiley-Interscience. pp. 9–60. ISBN 0-471-48004-5.
  7. ↑ Davis, Mackenzie Leo; et al. (2004). Principles of environmental engineering and science. 清华大学出版社. p. 133. ISBN 978-7-302-09724-2.
  8. ↑ Lengeler, Joseph W.; Drews, Gerhart; Schlegel, Hans Günter (1999). Biology of the Prokaryotes. Georg Thieme Verlag. p. 238. ISBN 978-3-13-108411-8.
  9. ↑ Dworkin, Martin (2006). The Prokaryotes: Ecophysiology and biochemistry (3rd ed.). Springer. p. 989. ISBN 978-0-387-25492-0.
  10. ↑ Bergey, David Hendricks; Holt, John G. (1994). Bergey's manual of determinative bacteriology (9th ed.). Lippincott Williams & Wilkins. p. 427. ISBN 978-0-683-00603-2.
  11. ↑ Corral, Paulina; Amoozegar, Mohammad A.; Ventosa, Antonio (2019-12-30). "Halophiles and Their Biomolecules: Recent Advances and Future Applications in Biomedicine". Marine Drugs. 18 (1): 33. Bibcode:2019MarDr..18...33C. doi:10.3390/md18010033. ISSN 1660-3397. PMC 7024382. PMID 31906001.
  12. ↑ Burgin, Amy J; Yang, Wendy H; Hamilton, Stephen K; Silver, Whendee L (February 2011). "Beyond carbon and nitrogen: how the microbial energy economy couples elemental cycles in diverse ecosystems". Frontiers in Ecology and the Environment. 9 (1): 44–52. Bibcode:2011FrEE....9...44B. doi:10.1890/090227. ISSN 1540-9295. Archived from the original on 2025-04-30.
  13. ↑ Banci, L., ed. (2013). Metallomics and the cell. Dordrecht: Springer. ISBN 978-94-007-5561-1. OCLC 841263185.
  14. 1 2 Madigan, Michael T.; Martinko, John M.; Stahl, David A.; Clark, David P. (2012). Brock biology of microorganisms (13th ed.). Boston: Benjamim Cummings. p. 1155. ISBN 978-0-321-64963-8.
  15. ↑ Bruslind, Linda (2019-08-01). "Chemolithotrophy & Nitrogen Metabolism". General Microbiology.
  16. ↑ Nazaries, Loïc; Murrell, J. Colin; Millard, Pete; Baggs, Liz; Singh, Brajesh K. (2013). "Methane, microbes and models: fundamental understanding of the soil methane cycle for future predictions". Environmental Microbiology. 15 (9): 2395–2417. Bibcode:2013EnvMi..15.2395N. doi:10.1111/1462-2920.12149. ISSN 1462-2920. PMID 23718889.
  17. 1 2 Buan, Nicole R. (2018-12-14). Robinson, Nicholas P. (ed.). "Methanogens: pushing the boundaries of biology". Emerging Topics in Life Sciences. 2 (4): 629–646. Bibcode:2018ETLS....2..629B. doi:10.1042/ETLS20180031. ISSN 2397-8554. PMC 7289024. PMID 33525834.
  18. ↑ Alemneh, Tewodros (2020-12-07). "Review on Methanogenesis and its Role". World Journal of Agriculture and Soil Science. 6 (2). doi:10.33552/WJASS.2020.06.000632.
  19. ↑ Conrad, Ralf (2020-02-01). "Importance of hydrogenotrophic, aceticlastic and methylotrophic methanogenesis for methane production in terrestrial, aquatic and other anoxic environments: A mini review". Pedosphere. 30 (1): 25–39. Bibcode:2020Pedos..30...25C. doi:10.1016/S1002-0160(18)60052-9. ISSN 1002-0160.
  20. 1 2 Ferry, James G. (2010-12-01). "The chemical biology of methanogenesis". Planetary and Space Science. 58 (14): 1775–1783. Bibcode:2010P&SS...58.1775F. doi:10.1016/j.pss.2010.08.014. ISSN 0032-0633.
  21. ↑ Oren, Aharon (2024-03-11). "On validly published names, correct names, and changes in the nomenclature of phyla and genera of prokaryotes: a guide for the perplexed". npj Biofilms and Microbiomes. 10 (1) 20. doi:10.1038/s41522-024-00494-9. ISSN 2055-5008. PMC 10928132. PMID 38467688.
  22. ↑ Nazaries, Loïc; Murrell, J. Colin; Millard, Pete; Baggs, Liz; Singh, Brajesh K. (2013-04-29). "Methane, microbes and models: fundamental understanding of the soil methane cycle for future predictions". Environmental Microbiology. 15 (9): 2395–2417. Bibcode:2013EnvMi..15.2395N. doi:10.1111/1462-2920.12149. ISSN 1462-2912. PMID 23718889.
  23. ↑ Biogeochemistry. 2020. doi:10.1016/C2017-0-00311-7. ISBN 978-0-12-814608-8. Retrieved 2026-02-27.
  24. ↑ Taubner, Ruth-Sophie; Schleper, Christa; Firneis, Maria G.; Rittmann, Simon K.-M. R. (2015-12-03). "Assessing the Ecophysiology of Methanogens in the Context of Recent Astrobiological and Planetological Studies". Life (Basel, Switzerland). 5 (4): 1652–1686. Bibcode:2015Life....5.1652T. doi:10.3390/life5041652. ISSN 2075-1729. PMC 4695842. PMID 26703739.
  25. 1 2 3 Guerrero-Cruz, Simon; Vaksmaa, Annika; Horn, Marcus A.; Niemann, Helge; Pijuan, Maite; Ho, Adrian (2021-05-14). "Methanotrophs: Discoveries, Environmental Relevance, and a Perspective on Current and Future Applications". Frontiers in Microbiology. 12 678057. doi:10.3389/fmicb.2021.678057. ISSN 1664-302X. PMC 8163242. PMID 34054786.
  26. ↑ Bueno de Mesquita, Clifton P.; Wu, Dongying; Tringe, Susannah G. (2023-01-24). "Methyl-Based Methanogenesis: an Ecological and Genomic Review". Microbiology and Molecular Biology Reviews. 87 (1): e00024–22. Bibcode:2023MMBR...8724.22B. doi:10.1128/mmbr.00024-22. PMC 10029344. PMID 36692297.
  27. ↑ Tomko, Paxton; Ovando-Ovando, Cesar Ivan; Boussagol, Pierre; Santiago-Martínez, Michel Geovanni; Visscher, Pieter T. (2026-04-01). "Methanogens Through Time and Space: Impact on Earth's Planetary Evolution and Biogeochemistry". Geosciences. 16 (4): 144. doi:10.3390/geosciences16040144. ISSN 2076-3263.
  28. 1 2 Nazaries, Loïc; Murrell, J. Colin; Millard, Pete; Baggs, Liz; Singh, Brajesh K. (29 April 2013). "Methane, microbes and models: fundamental understanding of the soil methane cycle for future predictions". Environmental Microbiology. 15 (9): 2395–2417. Bibcode:2013EnvMi..15.2395N. doi:10.1111/1462-2920.12149. ISSN 1462-2912. PMID 23718889.
  29. ↑ McInerney, Michael J.; Sieber, Jessica R.; Gunsalus, Robert P. (2009-11-10). "Syntrophy in anaerobic global carbon cycles". Current Opinion in Biotechnology. 20 (6): 623–632. doi:10.1016/j.copbio.2009.10.001. ISSN 1879-0429. PMC 2790021. PMID 19897353.
  30. ↑ Burgin, Amy J; Yang, Wendy H; Hamilton, Stephen K; Silver, Whendee L (2011). "Beyond carbon and nitrogen: how the microbial energy economy couples elemental cycles in diverse ecosystems". Frontiers in Ecology and the Environment. 9 (1): 44–52. Bibcode:2011FrEE....9...44B. doi:10.1890/090227. ISSN 1540-9295.
  31. ↑ Lyu, Zhe; Whitman, William B (2019-10-01). "Transplanting the pathway engineering toolbox to methanogens". Current Opinion in Biotechnology. Tissue, Cell and Pathway Engineering. 59: 46–54. doi:10.1016/j.copbio.2019.02.009. ISSN 0958-1669. OSTI 1567957. PMID 30875664.
  32. ↑ Enzmann, Franziska; Mayer, Florian; Rother, Michael; Holtmann, Dirk (2018-01-04). "Methanogens: biochemical background and biotechnological applications". AMB Express. 8 (1) 1. doi:10.1186/s13568-017-0531-x. ISSN 2191-0855. PMC 5754280. PMID 29302756.
  33. ↑ 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. doi:10.1016/j.bbabio.2013.12.002. ISSN 0005-2728. PMID 24333786.
  34. ↑ Offre, Pierre; Spang, Anja; Schleper, Christa (2013-09-08). "Archaea in Biogeochemical Cycles". Annual Review of Microbiology. 67: 437–457. doi:10.1146/annurev-micro-092412-155614. ISSN 0066-4227. PMID 23808334.
  35. ↑ Rivkina, Elizaveta; Shcherbakova, Viktoria; Laurinavichius, Kestas; Petrovskaya, Lada; Krivushin, Kirill; Kraev, Gleb; Pecheritsina, Svetlana; Gilichinsky, David (2007-07-01). "Biogeochemistry of methane and methanogenic archaea in permafrost: Methane and methanogenic archaea in permafrost". FEMS Microbiology Ecology. 61 (1): 1–15. doi:10.1111/j.1574-6941.2007.00315.x. PMID 17428301.
  36. ↑ Buan, Nicole R. (2018-12-14). "Methanogens: pushing the boundaries of biology". Emerging Topics in Life Sciences. 2 (4): 629–646. Bibcode:2018ETLS....2..629B. doi:10.1042/ETLS20180031. ISSN 2397-8554. PMC 7289024. PMID 33525834.

References

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1. Katrina Edwards. Microbiology of a Sediment Pond and the Underlying Young, Cold, Hydrologically Active Ridge Flank. Woods Hole Oceanographic Institution.

2. Coupled Photochemical and Enzymatic Mn(II) Oxidation Pathways of a Planktonic Roseobacter-Like Bacterium. Colleen M. Hansel and Chris A. Francis* Department of Geological and Environmental Sciences, Stanford University, Stanford, California 94305-2115. Received 28 September 2005. Accepted 17 February 2006.

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