Chemotroph

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]

Chemoautotroph

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

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, 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- and manganese-oxidizing bacteria

See also: Iron-oxidizing bacteria

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

Methanogens are chemotrophic archaea that produce methane as a byproduct of their metabolic processes.[16] Methanogens belong to the euryarchaeal domain.[17] Methanogens are a part of an ancient monophyletic lineage within Euryarcheota phylum and can be classified into three classes, six orders, twelve families and thirty-five genera.[18] Methanogenic metabolic pathways are thought to be present in some of the earliest organisms that survived on earth.[19] 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.[20][21]

Methanogens are identified by their ability when producing methane gas, to conserve energy needed to synthesize ATP (adenosine triphosphate, this difference is important to distinguish methanogens from other bacteria or archea that produce methane as a byproduct of metabolism.[21] Methanogenic archaea are involved in the late steps of degradation of organic matter, where they produce methane.[20][22] While different organisms may use different substrates, they all share methane as the final product of their metabolic processes, and they are all anaerobic processes.[20] Some examples of the type of substrates methanogens use are acetate, formate, methylamine and other small molecules as well as carbon dioxide and hydrogen gas.[23]Regardless of the substrate, all methanogenic bacteria utilize the enzyme methyl-coenzyme M reductase, which performs the final step of reducing methyl-coenzyme M to methane.[17][24]

See also

Notes

  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. 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. 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. 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. 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. 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. ^ a b 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. doi:10.1111/1462-2920.12149. ISSN 1462-2920.
  17. ^ a b Buan, Nicole R. (2018-12-14). "Methanogens: pushing the boundaries of biology". Emerging Topics in Life Sciences. 2 (4): 629–646. doi:10.1042/ETLS20180031. ISSN 2397-8554. PMC 7289024. PMID 33525834.
  18. ^ 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. doi:10.1111/1462-2920.12149. ISSN 1462-2912.
  19. ^ "Biogeochemistry". ScienceDirect. doi:10.1016/C2017-0-00311-7. Retrieved 2026-02-27.
  20. ^ a b c 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. doi:10.3389/fmicb.2021.678057. ISSN 1664-302X.
  21. ^ a b 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. doi:10.1042/ETLS20180031. ISSN 2397-8554. PMC 7289024. PMID 33525834.
  22. ^ Nazaries, Loïc; Murrell, J. Colin; Millard, Pete; Baggs, Liz; Singh, Brajesh K. (2013-05-29). "Methane, microbes and models: fundamental understanding of the soil methane cycle for future predictions". Environmental Microbiology. 15 (9): 2395–2417. doi:10.1111/1462-2920.12149. ISSN 1462-2912. Archived from the original on 2025-07-12.
  23. ^ 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.
  24. ^ 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. doi:10.1111/1462-2920.12149. ISSN 1462-2912.

References

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.

This article is issued from Wikipedia. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.