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The purple sulfur bacteria (PSB) are part of a group of Pseudomonadota capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in stratified water environments including hot springs, stagnant water bodies, as well as microbial mats in intertidal zones. Unlike plants, algae, and cyanobacteria, purple sulfur bacteria do not use water as their reducing agent, and therefore do not produce oxygen. Instead, they can use sulfur in the form of sulfide, or thiosulfate (as well, some species can use H2, Fe2+, or NO2−) as the electron donor in their photosynthetic pathways. The sulfur is oxidized to produce granules of elemental sulfur. This, in turn, may be oxidized to form sulfuric acid.
Thiobacillus is a genus of Gram-negative Betaproteobacteria. Thiobacillus thioparus is the type species of the genus, and the type strain thereof is the StarkeyT strain, isolated by Robert Starkey in the 1930s from a field at Rutgers University in the United States of America. While over 30 "species" have been named in this genus since it was defined by Martinus Beijerinck in 1904,, most names were never validly or effectively published. The remainder were either reclassified into Paracoccus, Starkeya ; Sulfuriferula, Annwoodia, Thiomonas ; Halothiobacillus, Guyparkeria, or Thermithiobacillus or Acidithiobacillus. The very loosely defined "species" Thiobacillus trautweinii was where sulfur oxidising heterotrophs and chemolithoheterotrophs were assigned in the 1910-1960s era, most of which were probably Pseudomonas species. Many species named in this genus were never deposited in service collections and have been lost.
Halothiobacillus is a genus in the Gammaproteobacteria. Both species are obligate aerobic bacteria; they require oxygen to grow. They are also halotolerant; they live in environments with high concentrations of salt or other solutes, but don't require them in order to grow.
Thermithiobacillus is a genus of nonsporeforming, rod-shaped, Gram-negative bacteria. The name derives from the Latin thermae, for warm baths, and the Classical Greek θείος, theios for sulfur. The type species of this genus was previously assigned to the genus Thiobacillus, but it was reclassified on the basis of 16S rRNA analysis in 2000, creating this genus.
The Halothiobacillaceae are a family of halotolerant, mesophilic, and obligate chemolithoautotrophic organisms in the Chromatiales comprising the genus Halothiobacillus. It is closely related to the family Thioalkalibacteraceae of halophilic obligate autotrophs with distinct morphological and genomic features.
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.
Thermithiobacillus tepidarius is a member of the Acidithiobacillia isolated from the thermal groundwaters of the Roman Baths at Bath, Somerset, United Kingdom. It was previously placed in the genus Thiobacillus. The organism is a moderate thermophile, 43–45 °C (109–113 °F), and an obligate aerobic chemolithotrophic autotroph. Despite having an optimum pH of 6.0–7.5, growth can continue to an acid medium of pH 4.8. Growth can only occur on reduced inorganic sulfur compounds and elementary sulfur, but unlike some species in other genus of the same family, Acidithiobacillus, Thermithiobacillus spp. are unable to oxidise ferrous iron or iron-containing minerals.
The outflow of acidic liquids and other pollutants from mines is often catalysed by acid-loving microorganisms; these are the acidophiles in acid mine drainage.
Bacillus pseudofirmus is a facultative anaerobe bacterium. It is a gram positive, alkaliphilic and alkalitolerant, aerobic endospore-forming bacteria.
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 versutus is an obligately alkaliphilic and obligately chemolithoautotrophic sulfur-oxidizing bacteria. It was first isolated from soda lakes in northern Russia.
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.
Thioalkalimicrobium is a defunct bacterial genus within the Gammaproteobacteria. All 4 species in the genus were reclassified to the genus Thiomicrospira in 2017.
Guyparkeria is a genus in the Gammaproteobacteria. Both species are obligate aerobic bacteria; they require oxygen to grow. They are also halophilic and have varying degrees of thermophilicity. They live in environments with high concentrations of salt or other solutes, such as in hydrothermal vent plumes or in hypersaline playas, and do require high sodium ion concentrations in order to grow, as is also the case in the other genus of the same family, Thioalkalibacter
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.
Thioalkalicoccus is a Gram-negative, mesophilic and obligate alkaliphilic genus of bacteria from the family of Chromatiaceae with one known species. Thioalkalicoccus limnaeus occurs in brackish water lakes.
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.
Alkalihalobacillus is a genus of gram-positive or gram-variable rod-shaped bacteria in the family Bacillaceae from the order Bacillales. The type species of this genus is Alkalihalobacillus alcalophilus.
References
- ↑ Banciu HL, Sorokin DY, Tourova TP, Galinski EA, Muntyan MS, Kuenen JG, Muyzer G (2008). "Influence of salts and pH on growth and activity of a novel facultatively alkaliphilic, extremely salt-tolerant, obligately chemolithoautotrophic sulfur-oxidizing Gammaproteobacterium Thioalkalibacter halophilus gen. nov., sp. nov. from South-Western Siberian soda lakes". Extremophiles. 12 (3): 391–404. doi:10.1007/s00792-008-0142-1. PMID 18309455. S2CID 17059634.
- 1 2 3 Boden R (2017). "Reclassification of Halothiobacillus hydrothermalis and Halothiobacillus halophilus to Guyparkeria gen. nov. in the Thioalkalibacteraceae fam. nov., with emended descriptions of the genus Halothiobacillus and family Halothiobacillaceae" (PDF). International Journal of Systematic and Evolutionary Microbiology. 67 (10): 3919–3928. doi: 10.1099/ijsem.0.002222 . hdl:10026.1/9982. PMID 28884673.