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The green sulfur bacteria are a phylum of obligately anaerobic photoautotrophic bacteria that metabolize sulfur.
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.
Purple bacteria or purple photosynthetic bacteria are Gram-negative proteobacteria that are phototrophic, capable of producing their own food via photosynthesis. They are pigmented with bacteriochlorophyll a or b, together with various carotenoids, which give them colours ranging between purple, red, brown, and orange. They may be divided into two groups – purple sulfur bacteria and purple non-sulfur bacteria (Rhodospirillaceae). Purple bacteria are anoxygenic phototrophs widely spread in nature, but especially in aquatic environments, where there are anoxic conditions that favor the synthesis of their pigments.
The Desulfobacteraceae are a family of Thermodesulfobacteriota. They reduce sulfates to sulfides to obtain energy and are strictly anaerobic. They have a respiratory and fermentative type of metabolism. Some species are chemolithotrophic and use inorganic materials to obtain energy and use hydrogen as their electron donor.
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 H2 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.
Desulfovibrio sulfodismutans is a bacterium. It grows under strictly anaerobic conditions by disproportionation of thiosulfate or sulfite to sulfate and sulfide. ThAc01 is its type strain.
Desulfonatronovibrio hydrogenovorans is a bacterium, the type species of its genus. It is an alkaliphilic, sulfate-reducing and motile bacterium. It is obligately sodium-dependent and its type strain is Z-7935.
Desulfocapsa sulfexigens is a mesophilic, anaerobic, gram-negative bacterium. It disproportionates elemental sulfur and thiosulfate. SB164P1 is its type strain.
Desulfovibrio oxyclinae is a bacterium. It is sulfate-reducing, and was first isolated from the upper 3mm layer of a hypersaline cyanobacterial mat in Sinai.
Desulfovibrio bastinii is a moderately halophilic bacteria. It is sulfate-reducing, mesophilic and motile. Its type strain is SRL4225T.
Desulfovibrio gracilis is a moderately halophilic bacteria. It is sulfate-reducing, mesophilic and motile. Its type strain is SRL6146T.
Desulfotomaculum arcticum is a spore-forming, moderately thermophilic, sulfate-reducing bacterium. Its type strain is 15T.
Desulfacinum hydrothermale is a thermophilic sulfate-reducing bacterium. Its cells are oval-shaped, 0.8–1 μm in width and 1.5–2.5 μm in length, motile and Gram-negative. The type strain is MT-96T.
Desulfovibrio halophilus is a halophilic sulfate-reducing bacterium.
Desulfovibrio gabonensis is a moderately halophilic sulfate-reducing bacterium. Its cells are motile curved rods that have a single polar flagellum. Its type strain is SEBR 2840.
Desulfonatronum thiodismutans is an alkaliphilic, sulfate-reducing bacterium capable of lithoautotrophic growth. It is Gram-negative, vibrio-shaped, with cells 0.6–0.7×1.2–2.7 μm in size, motile by a single polar flagellum. Its type strain is MLF1T.
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 energy-rich 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).
Thermodesulfobacterium hveragerdense is a bacterial species belonging to genus Thermodesulfobacterium, which are thermophilic sulfate-reducing bacteria. This species is found in aquatic areas of high temperature, and lives in freshwater like most, but not all Thermodesulfobacterium species It was first isolated from hotsprings in Iceland.
"CandidatusThiodictyon syntrophicum" is a gram-negative bacterium classified within purple sulfur bacteria (PSB). "Ca. T. syntrophicum" grows best under micro-oxic and low light conditions. There has only been one successful enrichment of "Ca. T. syntrophicum"; "Ca. T. syntrophicum" strain Cad16T.
References
- ↑ Janssen, P. H.; Schuhmann, Alexandra; Bak, F.; Liesack, Werner (1996). "Disproportionation of inorganic sulfur compounds by the sulfate-reducing bacterium Desulfocapsa thiozymogenes gen. nov., sp. nov". Archives of Microbiology. 166 (3): 184–192. doi:10.1007/s002030050374. ISSN 0302-8933. S2CID 23763422.
