Acetogen

An acetogen is a microorganism that generates acetate (CH3COO) as an end product of anaerobic respiration or fermentation. However, this term is usually employed in a narrower sense only to those bacteria and archaea that perform anaerobic respiration and carbon fixation simultaneously through the reductive acetyl coenzyme A (acetyl-CoA) pathway (also known as the Wood-Ljungdahl pathway).[1][2] These genuine acetogens are also known as "homoacetogens" and they can produce acetyl-CoA (and from that, in most cases, acetate as the end product) from two molecules of carbon dioxide (CO2) and four molecules of molecular hydrogen (H2). This process is known as acetogenesis,[3] and is different from acetate fermentation, although both occur in the absence of molecular oxygen (O2) and produce acetate. Although previously thought that only bacteria are acetogens, some archaea can be considered to be acetogens.[4]

Acetogens are found in a variety of habitats, generally those that are anaerobic (lack oxygen). Acetogens can use a variety of compounds as sources of energy and carbon; the best studied form of acetogenic metabolism involves the use of carbon dioxide as a carbon source and hydrogen as an energy source. Carbon dioxide reduction is carried out by the key enzyme acetyl-CoA synthase. Together with methane-forming archaea, acetogens constitute the last limbs in the anaerobic food web that leads to the production of methane from polymers in the absence of oxygen. Acetogens may represent ancestors of the first bioenergetically active cells in evolution.[5]

  1. ^ Schuchmann, Kai; Müller, Volker (2016-07-15). "Energetics and Application of Heterotrophy in Acetogenic Bacteria". Applied and Environmental Microbiology. 82 (14): 4056–4069. Bibcode:2016ApEnM..82.4056S. doi:10.1128/aem.00882-16. ISSN 0099-2240. PMC 4959221. PMID 27208103.
  2. ^ Berg, Ivan A.; Kockelkorn, Daniel; Ramos-Vera, W. Hugo; Say, Rafael F.; Zarzycki, Jan; Hügler, Michael; Alber, Birgit E.; Fuchs, Georg (2010-05-10). "Autotrophic carbon fixation in archaea". Nature Reviews Microbiology. 8 (6): 447–460. doi:10.1038/nrmicro2365. ISSN 1740-1534. PMID 20453874. S2CID 16059500.
  3. ^ Drake, H.; Gössner, A.; Daniel, S. (2008). "Old acetogens, new light". Annals of the New York Academy of Sciences. 1125 (1): 100–128. Bibcode:2008NYASA1125..100D. doi:10.1196/annals.1419.016. PMID 18378590. S2CID 24050060.
  4. ^ Henstra, Anne M; Sipma, Jan; Rinzema, Arjen; Stams, Alfons JM (2007). "Microbiology of synthesis gas fermentation for biofuel production". Current Opinion in Biotechnology. Energy biotechnology / Environmental biotechnology. 18 (3): 200–206. doi:10.1016/j.copbio.2007.03.008. ISSN 0958-1669. PMID 17399976.
  5. ^ Müller, Volker, and Frerichs, Janin(Sep 2013) Acetogenic Bacteria. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020086.pub2]