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The green sulfur bacteria are a phylum, Chlorobiota, of obligately anaerobic photoautotrophic bacteria that metabolize sulfur.
Propionic acid is a naturally occurring carboxylic acid with chemical formula CH
3CH
2CO
2H. It is a liquid with a pungent and unpleasant smell somewhat resembling body odor. The anion CH
3CH
2CO−
2 as well as the salts and esters of propionic acid are known as propionates or propanoates.
Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate (SO2−
4) as terminal electron acceptor, reducing it to hydrogen sulfide (H2S). Therefore, these sulfidogenic microorganisms "breathe" sulfate rather than molecular oxygen (O2), which is the terminal electron acceptor reduced to water (H2O) in aerobic respiration.
Ferroglobus is a genus of the Archaeoglobaceae.
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). 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, 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.
Sulfur-reducing bacteria are microorganisms able to reduce elemental sulfur (S0) to hydrogen sulfide (H2S). These microbes use inorganic sulfur compounds as electron acceptors to sustain several activities such as respiration, conserving energy and growth, in absence of oxygen. The final product of these processes, sulfide, has a considerable influence on the chemistry of the environment and, in addition, is used as electron donor for a large variety of microbial metabolisms. Several types of bacteria and many non-methanogenic archaea can reduce sulfur. Microbial sulfur reduction was already shown in early studies, which highlighted the first proof of S0 reduction in a vibrioid bacterium from mud, with sulfur as electron acceptor and H
2 as electron donor. The first pure cultured species of sulfur-reducing bacteria, Desulfuromonas acetoxidans, was discovered in 1976 and described by Pfennig Norbert and Biebel Hanno as an anaerobic sulfur-reducing and acetate-oxidizing bacterium, not able to reduce sulfate. Only few taxa are true sulfur-reducing bacteria, using sulfur reduction as the only or main catabolic reaction. Normally, they couple this reaction with the oxidation of acetate, succinate or other organic compounds. In general, sulfate-reducing bacteria are able to use both sulfate and elemental sulfur as electron acceptors. Thanks to its abundancy and thermodynamic stability, sulfate is the most studied electron acceptor for anaerobic respiration that involves sulfur compounds. Elemental sulfur, however, is very abundant and important, especially in deep-sea hydrothermal vents, hot springs and other extreme environments, making its isolation more difficult. Some bacteria – such as Proteus, Campylobacter, Pseudomonas and Salmonella – have the ability to reduce sulfur, but can also use oxygen and other terminal electron acceptors.
Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.
In biology, syntrophy, synthrophy, or cross-feeding is the phenomenon of one species feeding on the metabolic products of another species to cope up with the energy limitations by electron transfer. In this type of biological interaction, metabolite transfer happens between two or more metabolically diverse microbial species that live in close proximity to each other. The growth of one partner depends on the nutrients, growth factors, or substrates provided by the other partner. Thus, syntrophism can be considered as an obligatory interdependency and a mutualistic metabolism between two different bacterial species.
Dehalococcoides is a genus of bacteria within class Dehalococcoidia that obtain energy via the oxidation of hydrogen and subsequent reductive dehalogenation of halogenated organic compounds in a mode of anaerobic respiration called organohalide respiration. They are well known for their great potential to remediate halogenated ethenes and aromatics. They are the only bacteria known to transform highly chlorinated dioxins, PCBs. In addition, they are the only known bacteria to transform tetrachloroethene to ethene.
Propionyl-CoA is a coenzyme A derivative of propionic acid. It is composed of a 24 total carbon chain and its production and metabolic fate depend on which organism it is present in. Several different pathways can lead to its production, such as through the catabolism of specific amino acids or the oxidation of odd-chain fatty acids. It later can be broken down by propionyl-CoA carboxylase or through the methylcitrate cycle. In different organisms, however, propionyl-CoA can be sequestered into controlled regions, to alleviate its potential toxicity through accumulation. Genetic deficiencies regarding the production and breakdown of propionyl-CoA also have great clinical and human significance.
The Wood–Ljungdahl pathway is a set of biochemical reactions used by some bacteria. It is also known as the reductive acetyl-coenzyme A (Acetyl-CoA) pathway. This pathway enables these organisms to use hydrogen as an electron donor, and carbon dioxide as an electron acceptor and as a building block for biosynthesis.
Desulfobacter hydrogenophilus is a strictly anaerobic sulfate-reducing bacterium. It was isolated and characterized in 1987 by Friedrich Widdel of the University of Konstanz (Germany). Like most sulfate-reducing bacteria (SRB), D. hydrogenophilus is capable of completely oxidizing organic compounds (specifically acetate, pyruvate and ethanol) to CO2, and therefore plays a key role in biomineralization in anaerobic marine environments. However, unlike many SRB, D. hydrogenophilus is a facultative lithoautotroph, and can grow using H2 as an electron donor and CO2 as a carbon source. D. hydrogenophilus is also unique because it is psychrophilic (and has been shown to grow at temperatures as low as 0 °C or 32 °F). It is also diazotrophic, or capable of fixing nitrogen.
Desulfobulbus propionicus is a Gram-negative, anaerobic chemoorganotroph. Three separate strains have been identified: 1pr3T, 2pr4, and 3pr10. It is also the first pure culture example of successful disproportionation of elemental sulfur to sulfate and sulfide. Desulfobulbus propionicus has the potential to produce free energy and chemical products.
Pelobacter carbinolicus is a species of bacteria that ferments 2,3-butanediol and acetoin. It is Gram-negative, strictly anaerobic and non-spore-forming. Gra Bd 1 is the type strain. Its genome has been sequenced.
Pelobacter propionicus is a species of bacteria that ferments 2,3-butanediol and acetoin. It is Gram-negative, strictly anaerobic and non-spore-forming. Ott Bd 1 is the type strain.
Syntrophobacter fumaroxidans is a species of syntrophic propionate-degrading sulfate-reducing bacterium. Strain MPOBT is the type strain. Its genome has been fully sequenced.
Syntrophobacter pfennigii is a species of syntrophic propionate-oxidising anaerobic bacterium. Strain KoProp1 is the type strain.
Propionigenium modestum is a species of gram-negative, strictly anaerobic bacteria. It is rod-shaped and around 0.5-0.6 x 0.5-2.0μm in size. It is important in the elucidation of mechanism of ATP synthase.
Smithella propionica is a species of bacteria, the type species of its genus. It is anaerobic, syntrophic, propionate-oxidizing bacteria, with type strain LYPT.
Sulfoglycolysis is a catabolic process in primary metabolism in which sulfoquinovose (6-deoxy-6-sulfonato-glucose) is metabolized to produce energy and carbon-building blocks. Sulfoglycolysis pathways occur in a wide variety of organisms, and enable key steps in the degradation of sulfoquinovosyl diacylglycerol (SQDG), a sulfolipid found in plants and cyanobacteria into sulfite and sulfate. Sulfoglycolysis converts sulfoquinovose (C6H12O8S−) into various smaller metabolizable carbon fragments such as pyruvate and dihydroxyacetone phosphate that enter central metabolism. The free energy is used to form the high-energy molecules ATP (adenosine triphosphate) and NADH (reduced nicotinamide adenine dinucleotide). Unlike glycolysis, which allows metabolism of all carbons in glucose, some sulfoglycolysis pathways convert only a fraction of the carbon content of sulfoquinovose into smaller metabolizable fragments; the remaineder is excreted as C3-sulfonates 2,3-dihydroxypropanesulfonate (DHPS) or sulfolactate (SL); or the C2-sulfonate isethionate.
References
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- 1 2 3 4 Liu, Yitai; Balkwill, David L.; Aldrich, Henry C.; Drake, Gwendolyn R.; Boone, David R. (1999). "Characterization of the anaerobic propionate-degrading syntrophs Smithella propionica gen. nov., sp. nov. and Syntrophobacter wolinii". International Journal of Systematic and Evolutionary Microbiology. 49 (2): 545–556. doi: 10.1099/00207713-49-2-545 . ISSN 1466-5034. PMID 10319475.
- 1 2 Harmsen, Hermie J. M.; Wullings, Bart; Akkermans, Antoon D. L.; Ludwig, Wolfgang; Stams, Alfons J. M. (1993-09-01). "Phylogenetic analysis of Syntrophobacter wolinii reveals a relationship with sulfate-reducing bacteria". Archives of Microbiology. 160 (3): 238–240. doi:10.1007/BF00249130. ISSN 1432-072X. PMID 7692834. S2CID 22980988.
- ↑ Thauer, R K; Jungermann, K; Decker, K (1977-03-01). "Energy conservation in chemotrophic anaerobic bacteria". Bacteriological Reviews. 41 (1): 100–180. doi:10.1128/br.41.1.100-180.1977. PMC 413997 . PMID 860983.
- ↑ Yu, Ri-Qing; Reinfelder, John R.; Hines, Mark E.; Barkay, Tamar (2018-07-01). "Syntrophic pathways for microbial mercury methylation". The ISME Journal. 12 (7): 1826–1835. doi:10.1038/s41396-018-0106-0. ISSN 1751-7362. PMC 6018798 . PMID 29599522.
