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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.
A soda lake or alkaline lake is a lake on the strongly alkaline side of neutrality, typically with a pH value between 9 and 12. They are characterized by high concentrations of carbonate salts, typically sodium carbonate, giving rise to their alkalinity. In addition, many soda lakes also contain high concentrations of sodium chloride and other dissolved salts, making them saline or hypersaline lakes as well. High pH and salinity often coincide, because of how soda lakes develop. The resulting hypersaline and highly alkalic soda lakes are considered some of the most extreme aquatic environments on Earth.
Sulfurovum lithotrophicum is a species of bacteria, the type species of its genus. It is a sulfur-oxidizing chemolithoautotroph within the ε-Proteobacteria isolated from Okinawa Trough hydrothermal sediments. It is mesophilic and also oxidises thiosulfate. It is a Gram-negative, non-motile and coccoid to oval-shaped bacterium. The type strain is 42BKTT.
Thiomicrospira aerophila is an obligately alkaliphilic and obligately chemolithoautotrophic sulfur-oxidizing bacterium that was previously the type species of Thioalkalimicrobium prior to reclassification in 2017. It was first isolated from soda lakes in northern Russia.
Thiomicrospira siberica is a species of obligately alkaliphilic and obligately chemolithoautotrophic sulfur-oxidizing bacteria. It was first isolated from soda lakes in northern Russia, hence the specific epithet. In 2017, all 4 species of the genus Thioalkalimicrobium were reclassified to Thiomicrospira.
Thioalkalivibrio nitratis is an obligately alkaliphilic and obligately chemolithoautotrophic sulfur-oxidizing bacteria. It was first isolated from soda lakes in northern Russia.
Thioalkalivibrio denitrificancs is an obligately alkaliphilic and obligately chemolithoautotrophic sulfur-oxidizing bacteria. It was first isolated from soda lakes in northern Russia.
Thioalkalivibrio thiocyanoxidans is a species of alkaliphilic and obligately autotrophic sulfur-oxidizing bacterium. It was first isolated from soda lakes. Its type strain is Arh 2.
Thioalkalivibrio paradoxus is an alkaliphilic and obligately autotrophic sulfur-oxidizing bacteria. It was first isolated from soda lakes. Its type strain is ARh 1.
Desulfonatronovibrio thiodismutans is a species of haloalkaliphilic sulfate-reducing bacteria. It is able to grow lithotrophically by dismutation of thiosulfate and sulfite.
Thioalkalivibrio is a Gram-negative, mostly halophilic bacterial genus of the family Ectothiorhodospiraceae.
Thioalkalimicrobium is a defunct bacterial genus within the Gammaproteobacteria. All 4 species in the genus were reclassified to the genus Thiomicrospira in 2017.
Desulfonatronobacter is a bacteria genus from the family of Desulfobacteraceae.
The Thioalkalibacteraceae are a family of extremophiles, namely halophilic, alkaliphilic or alkalitolerant, mesophilic to thermophilic obligately chemolithoautotrophic organisms in the Chromatiales comprising the genus Thioalkalibacter and Guyparkeria. The family is closely related to the family Halothiobacillaceae of halotolerant, mesophilic obligate autotrophs.
Thiohalomonas is a moderately halophilic and obligately chemolithoautotrophic genus of purple sulfur bacteria.
Thiohalomonas denitrificans is a moderately halophilic, obligately chemolithoautotrophic and sulfur-oxidizing bacterium from the genus of Thiohalomonas which has been isolated from sediments of hypersaline lakes from Siberia in Russia.
Sedimenticola is a moderately halophilic and obligately chemolithoautotrophic, genus of bacteria from the class Gammaproteobacteria with one known species. Thiohalobacter thiocyanaticus has been isolated from sediments from hypersaline lakes from the Kulunda Steppe in Russia.
Natronoflexus is an obligately anaerobic and alkaliphilic genus of bacteria from the family of Marinilabiliaceae with one known species. Natronoflexus pectinivorans has been isolated from sediments from a soda lake from Altai in Russia.
Thiohalospira halophila is a halophilic, obligately chemolithoautotrophic and sulfur-oxidizing bacterium from the genus of Thiohalospira which has been isolated from a hypersaline lake from Siberia.
Ann Patricia Wood is a retired British biochemist and bacteriologist who specialized in the ecology, taxonomy and physiology of sulfur-oxidizing chemolithoautotrophic bacteria and how methylotrophic bacteria play a role in the degradation of odour causing compounds in the human mouth, vagina and skin. The bacterial genus Annwoodia was named to honor her contributions to microbial research in 2017.
References
- ↑ Sorokin DY, Lysenko AM, Mityushina LL, Tourova TP, Jones BE, Rainey FA, et al. (2001). "Thioalkalimicrobium aerophilum gen. nov., sp. nov. and Thioalkalimicrobium sibericum sp. nov., and Thioalkalivibrio versutus gen. nov., sp. nov., Thioalkalivibrio nitratis sp.nov., novel and Thioalkalivibrio denitrificancs sp. nov., novel obligately alkaliphilic and obligately chemolithoautotrophic sulfur-oxidizing bacteria from soda lakes". Int J Syst Evol Microbiol. 51 (Pt 2): 565–80. doi:10.1099/00207713-51-2-565. PMID 11321103.
