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In organochlorine chemistry, reductive dechlorination describes any chemical reaction which cleaves the covalent bond between carbon and chlorine via reductants, to release chloride ions. Many modalities have been implemented, depending on the application. Reductive dechlorination is often applied to remediation of chlorinated pesticides or dry cleaning solvents. It is also used occasionally in the synthesis of organic compounds, e.g. as pharmaceuticals.
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 or 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.
Halorespiration or dehalorespiration or organohalide respiration is the use of halogenated compounds as terminal electron acceptors in anaerobic respiration. Halorespiration can play a part in microbial biodegradation. The most common substrates are chlorinated aliphatics, chlorinated phenols and chloroform. Dehalorespiring bacteria are highly diverse. This trait is found in some Campylobacterota, Thermodesulfobacteriota, Chloroflexota, low G+C gram positive Clostridia, and ultramicrobacteria.
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.
In enzymology, a tetrachloroethene reductive dehalogenase is an enzyme that catalyzes the chemical reaction. This is a member of reductive dehalogenase enzyme family.
Shewanella oneidensis is a bacterium notable for its ability to reduce metal ions and live in environments with or without oxygen. This proteobacterium was first isolated from Lake Oneida, NY in 1988, hence its name.
The Chloroflexota are a phylum of bacteria containing isolates with a diversity of phenotypes, including members that are aerobic thermophiles, which use oxygen and grow well in high temperatures; anoxygenic phototrophs, which use light for photosynthesis ; and anaerobic halorespirers, which uses halogenated organics as electron acceptors.
Acetobacterium is a genus of anaerobic, Gram-positive bacteria that belong to the Eubacteriaceae family. The type species of this genus is Acetobacterium woodii. The name, Acetobacterium, has originated because they are acetogens, predominantly making acetic acid as a byproduct of anaerobic metabolism. Most of the species reported in this genus are homoacetogens, i.e. solely producing acetic acid as their metabolic byproduct. They should not be confused with acetic acid bacteria which are aerobic, Gram-negative Alphaproteobacteria.
Dehalococcoidia is a class of Chloroflexota, a phylum of Bacteria. It is also known as the DHC group.
Dehalobacter restrictus is a species of bacteria in the phylum Bacillota. It is strictly anaerobic and reductively dechlorinates tetra- and trichloroethene. It does not form spores; it is a small, gram-positive rod with one lateral flagellum. PER-K23 is its type strain.
Desulfitobacterium chlororespirans is a Gram-positive, anaerobic, spore-forming species of bacteria. Its type strain is Co23. It grows by coupling the oxidation of lactate to the reductive dechlorination of 3-chloro-4-hydroxybenzoate.
Desulfitobacterium hafniense is a species of gram positive bacteria, its type strain is DCB-2T..
Geobacter lovleyi is a gram-negative metal-reducing and tetrachloroethene-dechlorinating proteobacterium. It has potential as a bioremediation organism, and is actively researched as such.
Dehalogenimonas lykanthroporepellens is an anaerobic, Gram-negative bacteria in the phylum Chloroflexota isolated from a Superfund site in Baton Rouge, Louisiana. It is useful in bioremediation for its ability to reductively dehalogenate chlorinated alkanes.
Desulfitobacterium metallireducens is an anaerobic bacterium that couples growth to the reduction of metals and humic acids as well as chlorinated compounds. Its type strain is 853-15A(T). It was first isolated from a uranium-contaminated aquifer sediment.
Thermosyntropha lipolytica is a lipolytic, anaerobic, alkalitolerant, thermophilic bacteria. It lives in syntrophic coculture with a methanogen. Its cells are non-motile, non-spore forming, straight or slightly curved rods. Its type strain is JW/VS-265T.
Desulfovibrio dechloracetivorans is a bacterium. It is a Gram-negative, anaerobic, motile, short curved rod that grows by coupling the reductive dechlorination of 2-chlorophenol to the oxidation of acetate.
Adsorbable Organic Halides (AOX) is a measure of the organic halogen load at a sampling site such as soil from a land fill, water, or sewage waste. The procedure measures chlorine, bromine, and iodine as equivalent halogens, but does not measure fluorine levels in the sample.
Desulfuromonas is a Gram negative bacterial genus from the family of Desulfuromonadaceae. Desulfuromonas can reduce elemental sulfur to H2S. Desulfuromonas occur in anoxic sediments and saline lakes.
Reductive dehaholagenses (EC 1.97.1.8) are a group of enzymes utilized in organohalide respiring bacteria. These enzymes are mostly attached to the periplasmic side of the cytoplasmic membrane and play a central role in energy-conserving respiratory process for organohalide respiring bacteria by reducing organohalides. During such reductive dehalogenation reaction, organohalides are used as terminal electron acceptors. They catalyze the following general reactions:
References
- 1 2 Utkin I, Woese C, Wiegel J (October 1994). "Isolation and characterization of Desulfitobacterium dehalogenans gen. nov., sp. nov., an anaerobic bacterium which reductively dechlorinates chlorophenolic compounds". International Journal of Systematic Bacteriology. 44 (4): 612–9. doi: 10.1099/00207713-44-4-612 . PMID 7981092.
- ↑ Villemur R, Lanthier M, Beaudet R, Lépine F (September 2006). "The Desulfitobacterium genus". FEMS Microbiology Reviews. 30 (5): 706–33. doi: 10.1111/j.1574-6976.2006.00029.x . PMID 16911041.
- ↑ Gerritse J, Renard V, Pedro Gomes TM, Lawson PA, Collins MD, Gottschal JC (February 1996). "Desulfitobacterium sp. strain PCE1, an anaerobic bacterium that can grow by reductive dechlorination of tetrachloroethene or ortho-chlorinated phenols". Archives of Microbiology. 165 (2): 132–40. doi:10.1007/s002030050308. PMID 8593100. S2CID 29965475.
- ↑ Kruse T, van de Pas BA, Atteia A, Krab K, Hagen WR, Goodwin L, Chain P, Boeren S, Maphosa F, Schraa G, de Vos WM, van der Oost J, Smidt H, Stams AJ (March 2015). "Genomic, proteomic, and biochemical analysis of the organohalide respiratory pathway in Desulfitobacterium dehalogenans". Journal of Bacteriology. 197 (5): 893–904. doi:10.1128/JB.02370-14. PMC 4325113 . PMID 25512312.
- ↑ Kruse T, Goris T, Maillard J, Woyke T, Lechner U, de Vos W, Smidt H (December 2017). "Comparative genomics of the genus Desulfitobacterium". FEMS Microbiology Ecology. 93 (12). doi: 10.1093/femsec/fix135 . PMID 29040502.
