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In biochemistry, chemosynthesis is the biological conversion of one or more carbon-containing molecules and nutrients into organic matter using the oxidation of inorganic compounds or ferrous ions as a source of energy, rather than sunlight, as in photosynthesis. Chemoautotrophs, organisms that obtain carbon from carbon dioxide through chemosynthesis, are phylogenetically diverse. Groups that include conspicuous or biogeochemically-important taxa include the sulfur-oxidizing Gammaproteobacteria, the Campylobacterota, the Aquificota, the methanogenic archaea, and the neutrophilic iron-oxidizing bacteria.
Riftia pachyptila, commonly known as the giant tube worm, is a marine invertebrate in the phylum Annelida related to tube worms commonly found in the intertidal and pelagic zones. R. pachyptila lives on the floor of the Pacific Ocean near hydrothermal vents, the vents provide a natural ambient temperature in their environment ranging from 2 to 30 °C, at the same time it can tolerate extremely high hydrogen sulfide levels. These worms can reach a length of 3 m, and their tubular bodies have a diameter of 4 cm (1.6 in).
Chemotrophs are organisms that obtain energy by the oxidation of electron donors in their environments. These molecules can be organic (chemoorganotrophs) or inorganic (chemolithotrophs). The chemotroph designation is in contrast to phototrophs, which use solar energy. Chemotrophs can be either autotrophic or heterotrophic. Chemotrophs can be found on ocean floors where sunlight cannot reach. Or above ground, such as the case with iron bacteria.
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.
Hydrogen oxidizing bacteria are a group of facultative autotrophs that can use hydrogen as an electron donor.
Nautilia profundicola is a Gram-negative chemolithoautotrophic bacterium found around hydrothermal vents in the deep ocean. It was first discovered in 1999 on the East Pacific Rise at depth of 2,500 metres (8,200 ft), on the surface of the polychaete worm Alvinella pompejana. Nautilia profundicola lives symbiotically on the dorsal hairs of A. pompejana but they may also form biofilms and live independently on the walls of hydrothermal vents. The ability of N. profundicola to survive in an anaerobic environment rich in sulfur, H2 and CO2 of varying temperature makes it a useful organism to study, as these are the conditions that are theorized to have prevailed around the time of the earliest life on earth.
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.
Sulfurovum is a genus within the Campylobacterota which was first described in 2004 with the isolation and description of the type species Sulfurovum lithotrophicum from Okinawa trough hydrothermal sediments. Named for their ability to oxidize sulfur and their egg-like shape, cells are gram-negative, coccoid to short rods. Mesophilic chemolithoautotrophic growth occurs by oxidation of sulfur compounds coupled to the reduction of nitrate or molecular oxygen.
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.
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.
Balnearium lithotrophicum is a species of bacterium described in 2003 and classified as belonging to the Aquificota.
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.
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).
Lebetimonas is a genus of bacteria from the family Nautiliaceae.
Lebetimonas acidiphila is a thermophilic, acidophilic, hydrogen-oxidizing and motile bacterium from the genus of Lebetimonas. To observe growth there temperature should be between 30 and 68 degrees Celsius.
The hydrothermal vent microbial community includes all unicellular organisms that live and reproduce in a chemically distinct area around hydrothermal vents. These include organisms in the microbial mat, free floating cells, or bacteria in an endosymbiotic relationship with animals. Chemolithoautotrophic bacteria derive nutrients and energy from the geological activity at Hydrothermal vents to fix carbon into organic forms. Viruses are also a part of the hydrothermal vent microbial community and their influence on the microbial ecology in these ecosystems is a burgeoning field of research.
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.
Thioreductor is a Gram-negative, mesophilic, hydrogen-oxidizing, sulfur-reducing and motile genus of bacteria from the phylum Campylobacterota with one known species. Thioreductor micantisoli has been isolated from hydrothermal sediments from the Iheya North from the Mid-Okinawa Trough in Japan.
References
- ↑ Takai, K. (2006). "Sulfurimonas paralvinellae sp. nov., a novel mesophilic, hydrogen- and sulfur-oxidizing chemolithoautotroph within the Epsilonproteobacteria isolated from a deep-sea hydrothermal vent polychaete nest, reclassification of Thiomicrospira denitrificans as Sulfurimonas denitrificans comb. nov. and emended description of the genus Sulfurimonas". International Journal of Systematic and Evolutionary Microbiology. 56 (8): 1725–1733. doi: 10.1099/ijs.0.64255-0 . ISSN 1466-5026. PMID 16901999.
