Chemotroph#Chemoautotroph
{{Short description|Organisms that obtain energy by the oxidation of electron donors in their environments}}
A chemotroph is an organism that obtains energy by the oxidation of electron donors in their environments.{{cite news |last=Chang |first=Kenneth |title=Visions of Life on Mars in Earth's Depths |date=12 September 2016 |work=The New York Times |url=https://www.nytimes.com/2016/09/13/science/south-african-mine-life-on-mars.html |access-date=12 September 2016}} 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.{{cn|date=March 2025}}
Chemoautotroph
File:Blacksmoker in Atlantic Ocean.jpg 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 dramatically fast, such as Hydrogenovibrio crunogenus with a doubling time around one hour.{{cite journal |volume=187 |issue=16 |title=The Carbon-Concentrating Mechanism of the Hydrothermal Vent Chemolithoautotroph Thiomicrospira crunogena |year=2005 |journal=Journal of Bacteriology |pages=5761–5766 |last1=Dobrinski |first1=K. P. |pmid=16077123 |doi=10.1128/JB.187.16.5761-5766.2005 |pmc=1196061}}{{cite journal |author1=Rich Boden|author2= Kathleen M. Scott|author3= J. Williams|author4= S. Russel|author5= K. Antonen|author6= Alexander W. Rae|author7= Lee P. Hutt |title=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 |journal=International Journal of Systematic and Evolutionary Microbiology |volume=67 |issue=5 |pages=1140–1151 |date=June 2017 |pmid=28581925 |doi=10.1099/ijsem.0.001855 |doi-access=free |hdl=10026.1/8374 |hdl-access=free}}
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.{{cite book |last1=Kelly |first1=D. P. |last2=Wood |first2=A. P. |year=2006 |chapter=The Chemolithotrophic Prokaryotes |title=The Prokaryotes |pages=441–456 |publisher=Springer |location=New York |chapter-url=https://books.google.com/books?id=kyAZ47ZrazkC&pg=PA441 |isbn=978-0-387-25492-0 |doi=10.1007/0-387-30742-7_15}}{{cite book |last=Schlegel |first=H. G. |year=1975 |chapter=Mechanisms of Chemo-Autotrophy |title=Marine Ecology |volume=2, Part I |editor-first=O. |editor-last=Kinne |editor-link=Otto Kinne |pages=9–60 |publisher=Wiley-Interscience |isbn=0-471-48004-5 |chapter-url=https://www.int-res.com/archive/me_books/me_vol2_(physiological_mechanisms)_pt1.pdf#page=26}}
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.{{cite book |last=Davis |first=Mackenzie Leo |title=Principles of environmental engineering and science |year=2004 |publisher=清华大学出版社 |page=133 |isbn=978-7-302-09724-2 |display-authors=etal |url=https://books.google.com/books?id=e0OsNiQthNQC&q=chemoheterotroph&pg=PA133}}{{cite book |last1=Lengeler |first1=Joseph W. |last2=Drews |first2=Gerhart |last3=Schlegel |first3=Hans Günter |title=Biology of the Prokaryotes |year=1999 |publisher=Georg Thieme Verlag |page=238 |isbn=978-3-13-108411-8 |url=https://books.google.com/books?id=MiwpFtTdmjQC&q=chemolithoheterotroph+sulfur+bacteria&pg=PA238}}{{cite book |last=Dworkin |first=Martin |title=The Prokaryotes: Ecophysiology and biochemistry |year=2006 |edition=3rd |publisher=Springer |page=989 |isbn=978-0-387-25492-0 |url=https://books.google.com/books?id=uleTr2jKzJMC&q=chemolithoheterotroph+sulfur+bacteria&pg=PA989}}{{cite book |last1=Bergey |first1=David Hendricks |last2=Holt |first2=John G. |title=Bergey's manual of determinative bacteriology |year=1994 |edition=9th |publisher=Lippincott Williams & Wilkins |page=427 |isbn=978-0-683-00603-2 |url=https://books.google.com/books?id=jtMLzaa5ONcC&q=chemolithotrophic+sulfur+bacteria&pg=PA427}} Most animals and fungi are examples of chemoheterotrophs, as are halophiles.{{cn|date=March 2025}}
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.{{cite book |title=Metallomics and the cell |date=2013 |publisher=Springer |editor-first1=L. |editor-last1=Banci |isbn=978-94-007-5561-1 |location=Dordrecht |oclc=841263185 |url=https://search.worldcat.org/title/841263185}}
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. Iron is a trace element in marine environments.{{cite book |title=Brock biology of microorganisms |last1=Madigan |first1=Michael T. |last2=Martinko |first2=John M. |last3=Stahl |first3=David A. |last4=Clark |first4=David P. |date=2012 |publisher=Benjamim Cummings |isbn=978-0-321-64963-8 |edition=13th |location=Boston |pages=1155}} Its role as the electron donor for some chemolithotrophs is probably very ancient.{{cite book |last=Bruslind |first=Linda |date=2019-08-01 |title=General Microbiology |chapter=Chemolithotrophy & Nitrogen Metabolism |language=en |url=https://open.oregonstate.education/generalmicrobiology/chapter/chemolithotrophy-nitrogen-metabolism/}}
See also
- Chemosynthesis
- Lithotroph
- Methanogen (feeds on hydrogen)
- Methanotroph
- RISE project – expedition that discovered high-temperature vent communities
Notes
{{Reflist}}
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.
{{Modelling ecosystems}}