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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 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.
Campylobacterota are a phylum of bacteria. All species of this phylum are Gram-negative.
Sulfurimonas is a bacterial genus within the class of Campylobacterota, known for reducing nitrate, oxidizing both sulfur and hydrogen, and containing Group IV hydrogenases. This genus consists of four species: Sulfurimonas autorophica, Sulfurimonas denitrificans, Sulfurimonas gotlandica, and Sulfurimonas paralvinellae. The genus' name is derived from "sulfur" in Latin and "monas" from Greek, together meaning a “sulfur-oxidizing rod”. The size of the bacteria varies between about 1.5-2.5 μm in length and 0.5-1.0 μm in width. Members of the genus Sulfurimonas are found in a variety of different environments which include deep sea-vents, marine sediments, and terrestrial habitats. Their ability to survive in extreme conditions is attributed to multiple copies of one enzyme. Phylogenetic analysis suggests that members of the genus Sulfurimonas have limited dispersal ability and its speciation was affected by geographical isolation rather than hydrothermal composition. Deep ocean currents affect the dispersal of Sulfurimonas spp., influencing its speciation. As shown in the MLSA report of deep-sea hydrothermal vents Campylobacterota, Sulfurimonas has a higher dispersal capability compared with deep sea hydrothermal vent thermophiles, indicating allopatric speciation.
Deferribacter autotrophicus is an iron-reducing bacteria. It is thermophilic, anaerobic, chemolithoautotrophic, motile, straight to bent rod-shaped with one polar flagellum, 0.5–0.6 µm in width and 3.0–3.5 µm in length. The type strain is SL50T.
Thermodesulfobacterium hydrogeniphilum is a species of Sulfate-reducing bacteria. It is thermophilic, chemolithoautotrophic, non-spore-forming, marine species, with type strain SL6T.
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.
Hydrogenovibrio crunogenus is a colorless, sulfur-oxidizing bacterium first isolated from a deep-sea hydrothermal vent. It is an obligate chemolithoautotrophic sulfur oxidizer and differs from other species of this genus by its DNA base composition and by its growth rate and optimal pH in thiosulfate medium. ATCC 35932T is the type strain of the species. It was originally published in the genus Thiomicrospira as Thiomicrospira crunogena but was reclassified to the genus Hydrogenovibrio in 2017, resulting a grammatical gender change of the specific epithet from crunogena to crunogenus. The genome sequence of H. crunogenus XCL-2 has been published but that of the type strain has not yet been undertaken.
The Nautiliaceae are a family of bacteria placed in an order to itself, Nautiliales, or in the order Campylobacterales. The members of the family are all thermophilic. They are:
Palaeococcus ferrophilus is a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney. It cells are irregular cocci and motile with multiple polar flagella.
Thermococcus profundus is a hyperthermophilic archaeon isolated from a deep-sea hydrothermal vent. It is coccoid-shaped with 1–2 μm in diameter, designated as strain DT5432.
Sulfurimonas autotrophica is a sulfur- and thiosulfate-oxidizing bacterium. It is mesophilic, and its cells are short rods, each being motile by means of a single polar flagellum. Its genome has been sequenced.
Sulfurimonas paralvinellae is a hydrogen- and sulfur-oxidizing bacterium. It is a mesophilic chemolithoautotroph.
Caminibacter hydrogeniphilus is a species of thermophilic, hydrogen-oxidizing bacterium. It is anaerobic, rod-shaped, motile and has polar flagella. The type strain is AM1116T.
Persephonella guaymasensis is a thermophilic, hydrogen-oxidizing microaerophile first isolated from a deep-sea hydrothermal vent. It is strictly chemolithoautotrophic, microaerophilic, motile, 2-4 micrometres in size, rod-shaped, Gram-negative and non-sporulating. Its type strain is EX-H2T.
Nautilia lithotrophica is a thermophilic sulfur-reducing epsilon-proteobacterium isolated from a deep-sea hydrothermal vent. It is strictly anaerobic, with type strain 525T.
Deferribacter desulfuricans is a species of sulfur-, nitrate- and arsenate-reducing thermophile first isolated from a deep-sea hydrothermal vent. It is an anaerobic, heterotrophic thermophile with type strain SSM1T.
Methanothermococcus okinawensis is a thermophilic, methane-producing archaeon first isolated from deep-sea hydrothermal vent on the western Pacific Ocean. Its cells are highly motile, irregular cocci, with a polar bundle of flagella. Its type strain is IH1T. It grows at an optimal temperature of 60–65 °C and pH of 6.7. It is strictly anaerobic and reduces carbon dioxide with hydrogen to produce methane, but it can also use formate. Research studies indicate that it might be able to survive extreme conditions in solar system's other bodies, such as Saturn's moon Enceladus.
Parvibaculum hydrocarboniclasticum is an aerobic bacterium species from the genus of Parvibaculum which has been isolated from hydrothermal fluids from the East Pacific Rise in the Pacific Ocean. Parvibaculum hydrocarboniclasticum can use n-alkanes like octane, dodecane and hexadecane as a sole source for carbon and energy.
Caminibacter mediatlanticus is a Gram-negative, anaerobic, chemolithoautotrophic, thermophilic bacterium from the genus of Caminibacter which has been isolated from a hydrothermal vent from the Mid-Atlantic Ridge.
Nitratiruptor sp. is a genus of deep sea gram-negative Campylobacterota isolated from Iheya North Hydrothermal field in Okinawa Trough (Japan). This rod-shaped microorganism grows chemolithoautotrophically in a wide variety of electron donors and acceptors in absence of light and oxygen. It is also a thermophilic group capable of growing within the range of 37–65 °C with the optimal at 55 °C.
References
- ↑ Miroshnichenko, M. L. (2004). "Caminibacter profundus sp. nov., a novel thermophile of Nautiliales ord. nov. within the class 'Epsilonproteobacteria', isolated from a deep-sea hydrothermal vent". International Journal of Systematic and Evolutionary Microbiology. 54 (1): 41–45. doi: 10.1099/ijs.0.02753-0 . ISSN 1466-5026. PMID 14742457.
