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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.
Ferroplasma is a genus of Archaea that belong to the family Ferroplasmaceae. Members of the Ferroplasma are typically acidophillic, pleomorphic, irregularly shaped cocci.
Sulfolobaceae are a family of the Sulfolobales belonging to the domain Archaea. The family consists of several genera adapted to survive environmental niches with extreme temperature and low pH conditions.
In taxonomy, Acidianus is a genus of the Sulfolobaceae.
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.
Hydrogenobacter thermophilus is an extremely thermophilic, straight rod (bacillus) bacterium. TK-6 is the type strain for this species. It is a Gram negative, non-motile, obligate chemolithoautotroph. It belongs to one of the earliest branching order of Bacteria. H. thermophilus TK-6 lives in soil that contains hot water. It was one of the first hydrogen oxidizing bacteria described leading to the discovery, and subsequent examination of many unique proteins involved in its metabolism. Its discovery contradicted the idea that no obligate hydrogen oxidizing bacteria existed, leading to a new understanding of this physiological group. Additionally, H. thermophilus contains a fatty acid composition that had not been observed before.
Acidianus sulfidivorans is a species of archaeon. It is an extremely thermoacidophilic, obligately chemolithotrophic archaeon. It was first isolated from a solfatara on Lihir Island. Its cells are non-motile, Gram-negative, irregular-shaped cocci, 0.5-1.5 micrometres in size. It oxidises sulphur. The type strain is JP7(T).
Sulfolobus metallicus is a coccoid shaped thermophilic archaeon. It is a strict chemolithoautotroph gaining energy by oxidation of sulphur and sulphidic ores into sulfuric acid. Its type strain is Kra 23. It has many uses that take advantage of its ability to grow on metal media under acidic and hot environments.
Acidithiobacillus caldus formerly belonged to the genus Thiobacillus prior to 2000, when it was reclassified along with a number of other bacterial species into one of three new genera that better categorize sulfur-oxidizing acidophiles. As a member of the Gammaproteobacteria class of Pseudomonadota, A. caldus may be identified as a Gram-negative bacterium that is frequently found in pairs. Considered to be one of the most common microbes involved in biomining, it is capable of oxidizing reduced inorganic sulfur compounds (RISCs) that form during the breakdown of sulfide minerals. The meaning of the prefix acidi- in the name Acidithiobacillus comes from the Latin word acidus, signifying that members of this genus love a sour, acidic environment. Thio is derived from the Greek word thios and describes the use of sulfur as an energy source, and bacillus describes the shape of these microorganisms, which are small rods. The species name, caldus, is derived from the Latin word for warm or hot, denoting this species' love of a warm environment.
Acidithiobacillus thiooxidans, formerly known as Thiobacillus thiooxidans until its reclassification into the newly designated genus Acidithiobacillus of the Acidithiobacillia subclass of Pseudomonadota, is a Gram-negative, rod-shaped bacterium that uses sulfur as its primary energy source. It is mesophilic, with a temperature optimum of 28 °C. This bacterium is commonly found in soil, sewer pipes, and cave biofilms called snottites. A. thiooxidans is used in the mining technique known as bioleaching, where metals are extracted from their ores through the action of microbes.
Picrophilus oshimae is a species of Archaea described in 1996. Picrophilus oshimae was found in a fumarole in Hokkaido, Japan. The hot spring the fumarole was located in had a pH of 2.2.
Thermococcus stetteri is an extremely thermophilic, marine, sulfur-metabolizing archaebacterium. It is anaerobic, its cells being irregular cocci 1 to 2 μm in diameter. Of the strains first isolated, two were motile due to a tuft of flagella, while the other two strains were nonmotile. Its type strain is K-3. It can grow on starch, pectin, and peptides, but not amino acids.
Sulfolobus tokodaii is a thermophilic archaeon. It is acidophilic and obligately aerobic. The type strain is 7. Its genome has been sequenced.
Bacillus fumarioli is a species of aerobic endospore-forming bacteria. It is moderately thermophilic and acidophilic, with type strain LMG 17489T.
Chelatococcus sambhunathii is a gram-negative, aerobic catalase- and oxidase-positive motile bacteria with a single polar flagellum from the genus of Chelatococcus which was isolated from sediment of a hot sulfur spring in Orissa in India.
Ferrimicrobium acidiphilum is an extremely acidophilic and iron-oxidizing bacterium from the genus Ferrimicrobium which has been isolated from mine water from the Cae Coch sulfur mine in North Wales in England.
Microbial oxidation of sulfur is the oxidation of sulfur by microorganisms to build their structural components. The oxidation of inorganic compounds is the strategy primarily used by chemolithotrophic microorganisms to obtain energy to survive, grow and reproduce. Some inorganic forms of reduced sulfur, mainly sulfide (H2S/HS−) and elemental sulfur (S0), can be oxidized by chemolithotrophic sulfur-oxidizing prokaryotes, usually coupled to the reduction of oxygen (O2) or nitrate (NO3−). Anaerobic sulfur oxidizers include photolithoautotrophs that obtain their energy from sunlight, hydrogen from sulfide, and carbon from carbon dioxide (CO2).
Alicyclobacillus acidocaldarius is a species of Gram positive, strictly aerobic, bacterium. The bacteria are acidophilic, thermophilic, and produce endospores. The first identified strains of A. acidocaldarius were from geysers in Yellowstone National Park and fumerole soil in Hawaii Volcano National Park. The species was originally classified as Bacillus acidocaldarius in 1971, but further 16S rRNA studies found that the species belonged in the newly created genus Alicyclobacillus. The species name is derived from the Latin acidum (acid) and caldarius, referring to the acidic and high temperature environments from which it was first isolated. Thomas D. Brock was one of the researchers who first categorized the species; his discovery of Thermus aquaticus allowed for other researchers to discover Taq polymerase and polyermase chain reaction (PCR).
Alicyclobacillus dauci is a species of Gram positive, strictly aerobic, bacterium. The bacteria are acidophilic and produced endospores. It was first isolated from spoiled mixed vegetable and fruit juice. The species was first described in 2015, and the name is derived from the Latin dauci.
Sulfurisphaera tokodaii is a thermophilic archaeon of the Thermoproteota phylum. This species lives can grow as a chemoheterotroph and a lithoautotroph
References
- ↑ Segerer, A.; Neuner, A.; Kristjansson, J. K.; Stetter, K. O. (1986). "Acidianus infernus gen. nov., sp. nov., and Acidianus brierleyi Comb. nov.: Facultatively Aerobic, Extremely Acidophilic Thermophilic Sulfur-Metabolizing Archaebacteria". International Journal of Systematic Bacteriology. 36 (4): 559–564. doi: 10.1099/00207713-36-4-559 . ISSN 0020-7713.
