''Acidithiobacillus'' is a genus of the '' Acidithiobacillia'' in the "

Pseudomonadota Pseudomonadota (synonym Proteobacteria) is a major phylum of Gram-negative bacteria. The renaming of phyla in 2021 remains controversial among microbiologists, many of whom continue to use the earlier names of long standing in the literature. The ...

". The genus includes acidophilic organisms capable of iron and/or sulfur oxidation. Like all ''"Pseudomonadota"'', ''Acidithiobacillus'' spp. are

Gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

. They are also important generators of acid mine drainage, which is a major environmental problem around the world in

mining Mining is the extraction of valuable minerals or other geological materials from the Earth, usually from an ore body, lode, vein, seam, reef, or placer deposit. The exploitation of these deposits for raw material is based on the economic via ...

Genus ''Acidithiobacillus''

''Acidithiobacillus'' are acidophilic obligate autotrophs (''Acidithiobacillus caldus'' can also grow mixotrophically) that use elementary sulfur, tetrathionate and ferrous iron as electron donors. They assimilate carbon from carbon dioxide using the

transaldolase Transaldolase is an enzyme () of the non-oxidative phase of the pentose phosphate pathway. In humans, transaldolase is encoded by the ''TALDO1'' gene. The following chemical reaction is catalyzed by transaldolase: : sedoheptulose 7-phosph ...

variant of the

Calvin-Benson-Bassham cycle The Calvin cycle, light-independent reactions, bio synthetic phase, dark reactions, or photosynthetic carbon reduction (PCR) cycle of photosynthesis is a series of chemical reactions that convert carbon dioxide and hydrogen-carrier compounds into ...

. The genus comprises motile, rod-shaped cells that can be isolated from low pH environments including low pH microenvironments on otherwise neutral mineral grains.

Phylogeny

The order Acidithiobacillales (i.e. ''Thermithiobacillus'') were formerly members of the ''Gammaproteobacteria'', with considerable debate regarding their position and that they could also fall within the ''Betaproteobacteria'', but the situation was resolved by whole-genome alignment studies and both genera have been reclassified to the new class ''Acidithiobacillia''. Some members of this genus were classified as '' Thiobacillus'' spp., before they were reclassified in 2000. * ''Acidithiobacillus ferrooxidans'' (basonym ''Thiobacillus ferrooxidans'') can be isolated from iron-sulfur minerals such as

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...

deposits, oxidising

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

and

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula ...

as energy sources to support autotrophic growth and producing ferric iron and

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular formu ...

. * ''Acidithiobacillus thiooxidans'' (basonym ''Thiobacillus thiooxidans'', ''Thiobacillus concretivorus'') oxidises

and produces

; first isolated from the soil, it has also been observed causing biogenic sulfide corrosion of

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wi ...

sewer pipes by altering

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...

in sewage gas into sulfuric acid.

Bioleaching

Species within ''Acidothiobacillus'' are used in the biohydrometallurgy industry in methods called bioleaching and biomining, whereby metals are extracted from their ores through bacterial

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...

. Biomining uses radioactive waste as an ore with the bacteria to obtain gold, platinum, polonium, radon, radium, uranium, neptunium, americium, nickel, manganese, bromine, mercury, and their isotopes. ''Acidithiobacillus ferrooxidans'' has emerged as an economically significant bacterium in the field of biohydrometallurgy, in the leaching of sulfide ores since its discovery in 1950 by Colmer, Temple and Hinkle. The discovery of ''A. ferrooxidans'' led to the development of “ biohydrometallurgy”, which deals with all aspects of microbial mediated extraction of metals from minerals or solid wastes and acid mine drainage. ''A. ferrooxidans'' has been proven as a potent leaching organism, for dissolution of metals from low-grade sulfide ores. Recently, the attention has been focused upon the treatment of mineral concentrates, as well as complex sulfide ores using batch or continuous-flow reactors. ''Acidithiobacillus ferrooxidans'' is commonly found in acid mine drainage and mine

tailings In mining, tailings are the materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore. Tailings are different to overburden, which is the waste rock or other material that overlie ...

. The oxidation of ferrous iron and reduced sulfur oxyanions, metal sulfides and elementary sulfur results in the production of ferric sulfate in sulfuric acid, this in turn causes the solubilization of metals and other compounds. As a result, ''A. ferrooxidans'' may be of interest for bioremediation processes. ''Acidithiobacillus'' is also commonly abundant upon inner surfaces of sewers in areas exhibiting corrosion;

Genetic Sequencing Genetic Sequencing may refer to: * DNA sequencing * Whole genome sequencing Whole genome sequencing (WGS), also known as full genome sequencing, complete genome sequencing, or entire genome sequencing, is the process of determining the entiret ...

identifies ''Acidothiobacillus thiooxidans'' as the usual species present, although it is occasionally absent from such locations.Li, X., Kappler, U., Jiang, G., & Bond, P. L. (2017). The Ecology of Acidophilic Microorganisms in the Corroding Concrete Sewer Environment. Frontiers in microbiology, 8, 683. https://doi.org/10.3389/fmicb.2017.00683

Morphology

''Acidithiobacillus'' spp. occur as single cells or occasionally in pairs or chains, depending on growth conditions. Highly motile species have been described, as well as nonmotile ones. Motile strains have a single flagellum with the exception of ''A. albertensis'', which has a tuft of polar flagella and a glycocalyx. Nitrogen fixation also is an important ecological function carried out by some species in this genus, as is growth using molecular hydrogen as a source of energy - neither property is found in every species. Ferric iron can be used by some species as a terminal electron acceptor. *

References

External links