Acidithiobacillus
Encyclopedia
Acidithiobacillus is a genus of Proteobacteria
. Like all Proteobacteria, Acidithiobacillus is Gram-negative
. The members of this genus used to belong to Thiobacillus, before they were reclassified in the year 2000.
Both of these bacteria are used in a mining technique called bioleaching
whereby metals are extracted from their ores through oxidation. The bacteria are used as catalysts. It is also used in the biomining
process.
(i.e. Thermithiobacillus) have a problematic classification as it may be basal to a clade comprising the rest of the gammaproteobacterial species and the Betaproteobacteria, thus making the Gammaproteobacteria paraphyletic. Its relation to the Zetaproteobacteria is not clear.
Proteobacteria
The Proteobacteria are a major group of bacteria. They include a wide variety of pathogens, such as Escherichia, Salmonella, Vibrio, Helicobacter, and many other notable genera....
. Like all Proteobacteria, Acidithiobacillus is Gram-negative
Gram-negative
Gram-negative bacteria are bacteria that do not retain crystal violet dye in the Gram staining protocol. In a Gram stain test, a counterstain is added after the crystal violet, coloring all Gram-negative bacteria with a red or pink color...
. The members of this genus used to belong to Thiobacillus, before they were reclassified in the year 2000.
- Acidithiobacillus ferrooxidans (syn. Thiobacillus ferrooxidans) lives in pyritePyriteThe mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
deposits, metabolizing ironIronIron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
and sulfurSulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and producing sulfuric acidSulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
. - Acidithiobacillus thiooxidans (syn. Thiobacillus thiooxidans, Thiobacillus concretivorus) consumes sulfurSulfurSulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
and produces sulfuric acidSulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
. Though first isolated from the soil it has also been observed corroding concreteConcreteConcrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
sewerSanitary sewerA sanitary sewer is a separate underground carriage system specifically for transporting sewage from houses and commercial buildings to treatment or disposal. Sanitary sewers serving industrial areas also carry industrial wastewater...
pipes, altering hydrogen sulfideHydrogen sulfideHydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
sewage gas into sulfuric acidSulfuric acidSulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
.
Both of these bacteria are used in a mining technique called bioleaching
Bioleaching
Bioleaching is the extraction of specific metals from their ores through the use of living organisms. This is much cleaner than the traditional heap leaching using cyanide...
whereby metals are extracted from their ores through oxidation. The bacteria are used as catalysts. It is also used in the biomining
Biomining
Biomining is a new approach to the extraction of desired minerals from ores being explored by the mining industry in the past few years. Microorganisms are used to leach out the minerals, rather than the traditional methods of extreme heat or toxic chemicals, which have a deleterious effect on the...
process.
The genus Thiobacillus
Thiobacillus is the most important genus of chemolithotrophs that metabolize sulfur. It includes motile rod shaped cells that can be isolated from rivers, canals, acidified sulfate soils, mine drainage effluents and other mining areas. These Thiobacilli are adapted to wide variations of temperature and pH and can be readily isolated and enriched.Bioleaching
Among the group of Thiobacilli, Thiobacillus ferrooxidans has emerged as an economically significant bacterium in the field of leaching of sulfide ores since its discovery in 1950 by Colmer et al. The discovery of T. ferrooxidans led to the development of a new branch of metallurgical sciences called “biohydrometallurgy” which deals with all aspects of microbial mediated extraction of metals from minerals or solid wastes and acid mine drainage etc. (Torma, 1980). Acidithiobacillus 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.Morphology
Acidithioacillus ferrooxidans is an autotrophic, acidophilic, mesophile occurring in single or occasionally in pairs or chains, depending on growth conditions. Highly motile strains have been described as well as non-motile ones. Recent evidence indicate a high degree of genetic heterogeneity within the Acidithiobacillus ferrooxidans isolates, which are still probably misleadingly classified as a single species. Motile strains have a single flagellum & pili. The bacterium is non sporing and has a genome of about 2.8 × 106 base pairs and 55-65% of G-C content. Acidthiobacillus ferrooxidans grows at pH values of 4.5 to 1.3 in basal salt medium and derives its biosynthetic requirements by autotrophy using carbon from atmospheric carbon dioxide. Nitrogen fixation also is an important ecological function carried out by this bacterium in acidophilic habitats. Metabolic energy is derived aerobically by the oxidation of reduced inorganic sulfur compounds or ferrous ions. Anaerobic growth using elemental hydrogen or reduced inorganic sulfur compounds as electron donors and ferric ions as electron acceptors has also been discovered.Phylogeny
This genus and possibly the other genus in the order AcidithiobacillalesAcidithiobacillales
The Acidithiobacillales are a recently recognized order of Proteobacteria with only two genera, placed in separate families. Originally both were included in the genus Thiobacillus, but they are not related to the type species, which belongs to the beta proteobacteria....
(i.e. Thermithiobacillus) have a problematic classification as it may be basal to a clade comprising the rest of the gammaproteobacterial species and the Betaproteobacteria, thus making the Gammaproteobacteria paraphyletic. Its relation to the Zetaproteobacteria is not clear.