Thiosulfate (IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula S2O2−3. Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, such as sodium thiosulfate (Na2S2O3) and ammonium thiosulfate ((NH4)2S2O3). Thiosulfate salts occur naturally. Thiosulfate rapidly dechlorinates water, and is used to halt bleaching in the paper-making industry. Thiosulfate salts are mainly used for dyeing in textiles, and bleaching of natural substances.
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👉 Thiosulfate in the context of Hexasulfur
Hexasulfur is an inorganic chemical with the chemical formula S6. This allotrope was first prepared by M. R. Engel in 1891 by treating thiosulfate with HCl. Cyclo-S6 is orange-red and forms a rhombohedral crystal. It is called ρ-sulfur, ε-sulfur, Engel's sulfur and Aten's sulfur. Another method of preparation involves the reaction of a polysulfane with sulfur monochloride:
In this Dossier
- ⭐ Core Definition: Thiosulfate
- 👉 Thiosulfate in the context of Hexasulfur
- Thiosulfate in the context of Anaerobe
- Thiosulfate in the context of Sulfur cycle
- Thiosulfate in the context of Sulfate-reducing microorganism
- Thiosulfate in the context of Reverse Krebs cycle
- Thiosulfate in the context of Purple sulfur bacteria
Thiosulfate in the context of Anaerobe
An anaerobic organism or anaerobe is any organism that does not require molecular oxygen for its growth. It may react negatively or even die in the presence of free oxygen. Anaerobic organisms do not use oxygen as a terminal electron acceptor in their respiration process to produce energy, but a less powerful oxidizing agent, such as nitrate, ferric ion, Mn(IV), sulfate or bicarbonate anions. In contrast, an aerobic organism (aerobe) is an organism that requires a sufficiently oxygenated environment to respire, produce its energy, and thrive. Because the anaerobic energy production was the first mechanism to be used by living microorganisms in their evolution and is much less efficient than the aerobic pathway, anaerobes are practically, de facto, always unicellular organisms (e.g. bacteria and archaea (prokaryotes), or protozoans (eukaryotes). However, a minuscule multicellular organism, with an exceptionally rare metabolism and surviving in a hypersaline brine pool in the darkness of the bottom of the Mediterranean Sea, has been recently discovered. Meanwhile, it remains a scientific curiosity, as the much higher energy requirements of most multicellular organisms cannot be met by anaerobic respiration. Most fungi (eukaryotes) are obligate aerobes, requiring oxygen to survive and grow; however, some species, such as the Chytridiomycota that reside in the rumen of cattle, are obligate anaerobes; for these species, anaerobic respiration is used because oxygen would disrupt their metabolism or kill them. The deep seafloor and its underlying unconsolidated sediments ranks among the largest potential habitats for anaerobic microorganisms on Earth. Moreover, chemoautotroph microbes also thrive around hydrothermal vents, discharging hot water on the ocean seabed near mid-ocean ridges, where anaerobic conditions prevail. These microbes produce energy in the absence of sunlight or oxygen through a process called anaerobic respiration, whereby inorganic compounds and ions such as protons (H), elemental sulfur and its derivatives (SO2−4, S2O2−3), or ferric ions, are reduced to drive oxidative phosphorylation.
Thiosulfate in the context of Sulfur cycle
The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes.Steps of the sulfur cycle are:
- Mineralization of organic sulfur into inorganic forms, such as hydrogen sulfide (H2S), elemental sulfur, as well as sulfide minerals.
- Oxidation of hydrogen sulfide, sulfide, and elemental sulfur (S) to sulfate (SO
4). - Reduction of sulfate to sulfide.
- Incorporation of sulfide into organic compounds (including metal-containing derivatives).
- Disproportionation of sulfur compounds (elemental sulfur, sulfite, thiosulfate) into sulfate and hydrogen sulfide.
Thiosulfate in the context of Sulfate-reducing microorganism
Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate (SO
4) as terminal electron acceptor, reducing it to hydrogen sulfide (H2S). Therefore, these sulfidogenic microorganisms "breathe" sulfate rather than molecular oxygen (O2), which is the terminal electron acceptor reduced to water (H2O) in aerobic respiration.
Most sulfate-reducing microorganisms can also reduce some other oxidized inorganic sulfur compounds, such as sulfite (SO
3), dithionite (S
2O
4), thiosulfate (S
2O
3), trithionate (S
3O
6), tetrathionate (S
4O
6), elemental sulfur (S8), and polysulfides (S
n). Other than sulfate reduction, some sulfate-reducing microorganisms are also capable of other reactions like disproportionation of sulfur compounds. Depending on the context, "sulfate-reducing microorganisms" can be used in a broader sense (including all species that can reduce any of these sulfur compounds) or in a narrower sense (including only species that reduce sulfate, and excluding strict thiosulfate and sulfur reducers, for example).
Thiosulfate in the context of Reverse Krebs cycle
The reverse Krebs cycle (also known as the reverse tricarboxylic acid cycle, the reverse TCA cycle, or the reverse citric acid cycle, or the reductive tricarboxylic acid cycle, or the reductive TCA cycle) is a sequence of chemical reactions that are used by some bacteria and archaea to produce carbon compounds from carbon dioxide and water by the use of energy-rich reducing agents as electron donors.
The reaction is the citric acid cycle run in reverse. Where the Krebs cycle takes carbohydrates and oxidizes them to CO2 and water, the reverse cycle takes CO2 and H2O to make carbon compounds.This process is used by some bacteria (such as Aquificota) to synthesize carbon compounds, sometimes using hydrogen, sulfide, or thiosulfate as electron donors. This process can be seen as an alternative to the fixation of inorganic carbon in the Calvin cycle which occurs in a wide variety of microbes and higher organisms.
Thiosulfate in the context of Purple sulfur bacteria
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 the electron donor in their photosynthetic pathways. Some species can use H2, Fe, or NO2 as well. The sulfur is oxidized to produce granules of elemental sulfur. This, in turn, may be oxidized to form sulfuric acid.
The purple sulfur bacteria are largely divided into two families, the Chromatiaceae and the Ectothiorhodospiraceae, which produce internal and external sulfur granules respectively, and show differences in the structure of their internal membranes. They make up part of the order Chromatiales, included in the Gammaproteobacteria. The genus Halothiobacillus is also included in the Chromatiales, in its own family, but it is not photosynthetic.