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Original - "Syntrophy"
Syntrophy
[edit]
Syntrophy, synthrophy,[1] cross-feeding, or cross feeding [Greek syn meaning together, trophe meaning nourishment] is the phenomenon that one species lives off the products of another species. In this association, the growth of one partner is improved, or depends on the nutrients, growth factors or substrate provided by the other partner.
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The defining feature of ruminants, such as cows and goats, is a stomach called a rumen which contains billions of microbes, many of which are syntrophic. One excellent example of this syntrophy is interspecies hydrogen transfer. Some anaerobic fermenting microbes in the rumen (and other gastrointestinal tracts) are capable of degrading organic matter to short chain fatty acids, and hydrogen.[2] The accumulating hydrogen inhibits the microbe's ability to continue degrading organic matter, but syntrophic hydrogen-consuming microbes allow continued growth.[3] In addition, fermentative bacteria gain maximum energy yield when protons are used as electron acceptor with concurrent H2 production.[4][5] Hydrogen-consuming organisms include methanogens, sulfate-reducers, acetogens, and others.[2] Some fermentation products, such as fatty acids longer than two carbon atoms, alcohols longer than one carbon atom, and branched-chain and aromatic fatty acids, cannot directly be used in methanogenesis. In acetogenesis process, these products are oxidized to acetate and H2 by obligated proton reducing bacteria in syntrophic relationship with methanogenic archaea as low H2 partial pressure is essential for acetogenic reactions to be thermodynamically favorable (ΔG < 0).[5] (Stams et al., 2005)
Edits - "Syntrophy"
Syntrophy
[edit]
Syntrophy, synthrophy,[1] cross-feeding, or cross feeding [Greek syn meaning together, trophe meaning nourishment] is a form of metabolic interaction between two microorganisms that depend on metabolic processes of their partners. This occurs to maintain their own energetically favourable metabolism, further resulting in a mutually beneficial relation.[6]
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Metabolic mechanism
[edit]The main motive behind a syntrophic relation between two bacterial organisms is generalized as a relationship where each participant's metabolic activity cannot independently overcome the thermodynamic pressure of the reaction under standard conditions even when a cosubstrate or nutrient is added into the environment. Therefore, the cooperation of the other participant is required to reduce the intermediate pool size.[5]
The Methanobacillus omelianskii culture is a classic example in demonstrating how two separate unfavourable reactions can be carried out by syntrophic interactions.[7] Strain S and strain M.o.H of Methanobacillus omelianskii oxidize ethanol into acetate and methane by a process called interspecies hydrogen transfer. Individuals of strain S are observed as obligate anaerobic bacteria that use ethanol as an electron donor, whereas organisms of strain M.o.H are methanogens that oxidize hydrogen gas to produce methane.[3][8] These two metabolic reactions can be shown as follows:
- Strain S: 2 CH3CH2OH + 2 H2O → 2 CH3COO- + 2 H+ + 4 H2 (ΔG°' = +19 kJ)
- Strain M.o.H.: 4 H2 + CO2 → CH4 + 2 H2O (ΔG°' = -131 kJ)[5][9]
Complex organic compounds such as ethanol, propionate, butyrate, and lactate cannot be directly used as substrates for methanogenesis by methanogens. On the other hand, fermentation of these organic compounds cannot occur in fermenting microorganisms unless the hydrogen concentration is reduced to a low level by the methanogens.[10] In this case, hydrogen, an electron-carrying compound (mediator) is transported from the fermenting bacteria to the methanogen through a process called mediated interspecies electron transfer (MIET), where the mediator is carried down a concentration gradient created by a thermodynamically favourable coupled redox reaction.[11] Yinghuang237 (talk) 18:56, 6 October 2017 (UTC)
- ^ a b Wang, Lawrence; Ivanov, Volodymyr; Tay, Joo-Hwa; Hung, Yung-Tse (5 April 2010). Environmental Biotechnology Volume 10. Springer Science & Business Media. p. 127. ISBN 978-1-58829-166-0. Retrieved 3 March 2015.
- ^ a b Nakamura, Noriko; Lin, Henry C.; McSweeney, Christopher S.; Mackie, Roderick I.; Gaskins, H. Rex (2010-01-01). "Mechanisms of microbial hydrogen disposal in the human colon and implications for health and disease". Annual Review of Food Science and Technology. 1: 363–395. doi:10.1146/annurev.food.102308.124101. ISSN 1941-1413. PMID 22129341.
- ^ a b Bryant, M. P.; Wolin, E. A.; Wolin, M. J.; Wolfe, R. S. (1967-03-01). "Methanobacillus omelianskii, a symbiotic association of two species of bacteria". Archiv für Mikrobiologie. 59 (1–3): 20–31. doi:10.1007/BF00406313. ISSN 0003-9276. PMID 5602458.
- ^ Dolfing, Jan; Tiedje, James M. (1986-11-01). "Hydrogen cycling in a three-tiered food web growing on the methanogenic conversion of 3-chlorobenzoate". FEMS Microbiology Ecology. 2 (5): 293–298. doi:10.1111/j.1574-6968.1986.tb01740.x. ISSN 1574-6941.
- ^ a b c d Schink, B. (1997-06-01). "Energetics of syntrophic cooperation in methanogenic degradation". Microbiology and Molecular Biology Reviews. 61 (2): 262–280. ISSN 1092-2172. PMC 232610. PMID 9184013.
- ^ Sieber, Jessica R.; McInerney, Michael J.; Gunsalus, Robert P. (2012). "Genomic Insights into Syntrophy: The Paradigm for Anaerobic Metabolic Cooperation". Annual Review of Microbiology. pp. 429–452. doi:10.1146/annurev-micro-090110-102844.
- ^ Morris, Brandon E.L.; Henneberger, Ruth; Huber, Harald; Moissl-Eichinger, Christine (2013). "Microbial syntrophy: interaction for the common good". FEMS Microbiol Rev. 37 (3): 384–406. doi:10.1111/1574-6976.12019.
{{cite journal}}: Cite has empty unknown parameter:|1=(help) - ^ McInerney, Michael J.; Struchtemeyer, Christopher G.; Sieber, Jessica; Mouttaki, Housna; Stams, Alfons J. M.; Schink, Bernhard; Rohlin, Lars; Gunsalus, Robert P. (1 March 2008). "Physiology, Ecology, Phylogeny, and Genomics of Microorganisms Capable of Syntrophic Metabolism". Annals of the New York Academy of Sciences. pp. 58–72. doi:10.1196/annals.1419.005.
- ^ Drake, Harold L.; Horn, Marcus A.; Wüst, Pia K. (1 October 2009). "Intermediary ecosystem metabolism as a main driver of methanogenesis in acidic wetland soil". Environmental Microbiology Reports. pp. 307–318. doi:10.1111/j.1758-2229.2009.00050.x.
- ^ Stams, Alfons J. M.; De Bok, Frank A. M.; Plugge, Caroline M.; Van Eekert, Miriam H. A.; Dolfing, Jan; Schraa, Gosse (1 March 2006). "Exocellular electron transfer in anaerobic microbial communities". Environmental Microbiology. pp. 371–382. doi:10.1111/j.1462-2920.2006.00989.x.
- ^ Storck, Tomas; Virdis, Bernardino; Batstone, Damien J. (2016). "Modelling extracellular limitations for mediated versus direct interspecies electron transfer". The ISME journal. pp. 621–631. doi:10.1038/ismej.2015.139.