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37-401: Acidithiobacillus albertensis Acidithiobacillus caldus Acidithiobacillus cuprithermicus Acidithiobacillus ferrianus Acidithiobacillus ferridurans Acidithiobacillus ferriphilus Acidithiobacillus ferrivorans Acidithiobacillus ferrooxidans Acidithiobacillus sulfuriphilus Acidithiobacillus thiooxidans Acidithiobacillus is a genus of

74-411: A broad range of conditions, including acidic pH levels and temperature, with the best growth occurring at a pH of 2.0 to 2.5 and a temperature of 45 °C. Optimal growth results in a short generation time of 2–3 hours, depending on the environmental factors present. A. caldus is not considered to be halophilic because it displayed no signs of growth in environments containing NaCl . A. caldus

111-778: A length of 2,932,225 base pairs, the genomic sequence of A. caldus is GC-rich with a GC content (mol%) in the range of 63.1-63.9% for strain KU and 61.7% for strain BC13. DNA hybridization studies have revealed that strains KU and BC13 exhibited 100% homology with each other, yet showed no DNA hybridization of significance (2-20%) with other species in the genus including A. ferrooxidans and A. thiooxidans , or with other similar Pseudomonadota , such as Thiomonas cuprina or Thiobacillus thioparus . Strains of A. caldus have been differentiated from other related acidithiobacilli, including A. ferrooxidans and A. thiooxidans , by sequence analyses of

148-410: A nearly neutral level of 6.5. Certain strains, including KU and BC13, have been found to display signs of growth in a broad, acidic pH range, with a slow growth rate involving a longer generation time , about 45 hours, at a pH of 4.0 and a rate of 6–7 hours at a pH of 1.0. A. caldus has its shortest generation time of 2–3 hours in conditions involving a pH between 2.0 and 2.5. No growth was observed at

185-484: A pH of 0.5, showing that some conditions are simply too acidic to support the growth of even extreme acidophiles. A. caldus is capable of oxidizing reduced inorganic sulfur compounds along with other substrates including molecular hydrogen , and formate , in addition to numerous organic compounds and sulfide minerals . It displays chemolithotrophic growth when exposed to substrates containing sulfur, tetrathionate , or thiosulfate , with sulfate being produced as

222-458: A significant practical application in the industrial field of biomining and mineral biotechnology, contributing to the enhanced recovery of desired minerals from rocks known as ores . Metals such as gold have been recovered from ores which contain pyrite (also known as fool's gold ) and arsenopyrite , two sulfide minerals that are often associated with considerable amounts of this precious metal. Biomining refers to both biooxidation, where

259-413: A typical Gram-negative cell wall. It is about 1 by 1-2 μm in length and frequently is found in pairs. Different strains have been shown to vary in size when compared to one another. One of the smaller strains, BC13, has a diameter around 0.7 μm and is about 1.2 μm in length, whereas strain KU is a little longer, with a diameter of roughly 0.8 μm and a length around 1.8 μm. A. caldus displays tolerance to

296-417: Is a significantly diverse genus, species have adapted to survive in differing environments under varying limitations such as acidity, temperature, and nutrient availability. For example A. caldus, which is the only known thermoacidophile of the genus, is adept to survive in extreme temperatures up to 52°C, while A. ferrooxidans can survive under extremely acidic conditions with pH <1. Metabolic traits of

333-568: 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. Acidithiobacillus spp. are known to inhabit diverse environments such as hot springs, acid mine drainage ( abandoned mine drainage ) or mine tailings , acidic soils, and sulfidic caves. Terrestrial hot springs are currently an important research focus as they can provide known limiting conditions for

370-517: Is capable of oxidizing reduced inorganic sulfur compounds (RISCs) that form during the breakdown of sulfide minerals. The meaning of the prefix acidi- in the name Acidithiobacillus comes from the Latin word acidus , signifying that members of this genus love a sour, acidic environment. Thio is derived from the Greek word thios and describes the use of sulfur as an energy source, and bacillus describes

407-549: Is commonly found in acid mine drainage and mine tailings . 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 identifies Acidothiobacillus thiooxidans as

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444-409: Is moderately thermophilic and thrives at an optimum temperature of 45 °C. Certain strains, such as strain KU, have still been shown to exhibit growth on a tetrathionate medium in conditions with a temperature range as low as 32 °C and as high as 52 °C. When grown on a medium containing sulfur, strain BC13 has been found to tolerate temperatures as high as 55 °C. A genetic basis

481-450: Is the most widely studied of the genus, but A. caldus and A. thiooxidans are also significant in research. Like all "Pseudomonadota" , Acidithiobacillus spp. are Gram-negative and non-spore forming. They also play a significant role in the generation of acid mine drainage ; a major global environmental challenge within the mining industry. Some species of Acidithiobacillus are utilized in bioleaching and biomining . A portion of

518-425: Is then used to carry out sulfur oxidization, which provides an essential energy source for important cellular metabolic functions Biohydrometallurgy Hydrometallurgy refers to a specific process involving the chemical properties of water to create an aqueous solution for metal extraction through a series of chemical reactions Biohydrometallurgy represents the overlap of the world of microorganisms to

555-449: Is thought to exist for the extreme temperature tolerance shown by A. caldus as compared to other species in its genus, such as A. ferrooxidans and A. thiooxidans . As with all acidophilic microorganisms, A. caldus thrives best in an environment with a low, acidic pH with a preferred pH range of 2.0-2.5. This microorganism is capable of coping with a large pH gradient across the cellular membrane, keeping its intracellular pH around

592-463: Is ubiquitous among the genus, iron oxidation is specific to A. ferrooxidans, A. ferridurans, A. ferriphilus, A. ferrivorans, and A. ferrianus. The transition to modern day Acidithiobacillus spp. has occurred over hundred of millions of years involving events of gene gain and gene loss. Some evidence points to the most recent common ancestor of Acidithiobacillus appearing around the same time as A. caldus , 800 million years ago. Acidithiobacillus

629-616: The Acidithiobacillia class include the presence of enzymes which aid in the use of hydrogen sulfide, elemental sulfur, thiosulfate, and tetrathionate in sulfur metabolism. Species capable of iron oxidation also possess genes that are coded for nitrogen fixation and hydrogen utilization. The diversity in genomic composition allows these same species to inhabit both aerobic and anaerobic environments. Acidithiobacillus caldus Thiobacillus caldus (Hallberg & Lindstrom 1994) Acidithiobacillus caldus formerly belonged to

666-497: The Acidithiobacillia in the phylum " Pseudomonadota ". This genus includes ten species of acidophilic microorganisms capable of sulfur and/or iron oxidation: Acidithiobacillus albertensis, Acidithiobacillus caldus, Acidithiobacillus cuprithermicus, Acidithiobacillus ferrianus, Acidithiobacillus ferridurans, Acidithiobacillus ferriphilus, Acidithiobacillus ferrivorans, Acidithiobacillus ferrooxidans, Acidithiobacillus sulfuriphilus, and Acidithiobacillus thiooxidans. A. ferooxidans

703-653: 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. 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 . Biomining uses radioactive waste as an ore with

740-597: The PCR -amplified 16S - 23S rDNA intergenic spacer (ITS) and restriction fragment length polymorphism . Phylogenetic analysis of ITS sequences was sufficient to differentiate three unique species of Acidithiobacillus that were found to have slightly different physiological tolerances. The 16S-23S rDNA spacer region is a useful target for developing molecular methods that focus on the detection, rapid differentiation, and identification of Acidithiobacillus species. Since its discovery in 1994, A. caldus has been found to have

777-408: The ability to oxidize sulfidic ores and thereby solubilize metals. This ability has contributed to a general public interest in this microorganism because of its application in the industrial bioleaching of metals from ores and because of its effective means by which to recover precious metals . Bacteria involved in bioleaching function primarily to produce Fe from the oxidation of ferrous iron, which

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814-452: The acid hydrolysis of casein ), nor a 2.5 mM concentration of glucose as the sole substrate have been shown to induce heterotrophic growth of A. caldus . Instead, growth is seen to occur mixotrophically with tetrathionate and yeast extract or glucose. Strain BC13 is capable of growth on a glucose medium, but not after being transferred to a glucose medium from one that contained sulfur in addition to glucose. Key intermediates in

851-569: The alpha-, beta-, and gamma-classes of the Pseudomonadota. Thiobacillus species exhibit a tremendous amount of diversity in physiology and DNA composition, which was one reason for reclassification of this species into a new genus containing four species of acidophiles (microorganisms which function best in an acidic environment), some of which are also capable of oxidizing iron[II] and sulfide minerals . A. caldus , originally isolated from spoils of unneeded rocks encountered when mining coal,

888-409: 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

925-471: The basis by which they can survive in low pH environments likely evolved through vertical gene transfer . It is probable that the foundational genes of acid resistance in Acidithiobacillus were first inherited from a neutrophile , possibly thermophilic, and throughout their evolutionary history further acid resistance genes were obtained from neighboring acidophiles . While the trait of sulfur oxidation

962-481: 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

999-567: The end product. Reduced sulfur compounds are used by A. caldus to support its autotrophic growth in an environment which lacks sunlight. The growth of A. caldus is enhanced when the air used for sparging , a process by which bubbles of a chemically inert gas are pumped through a liquid, is supplemented with 2% (w/v) CO 2 . Neither 0.05% yeast extract (a yeast product formed when a cell's walls are removed and its internal contents are extracted ), casamino acids (an amino acid / peptide mixture common to microbial growth media formed from

1036-619: The environment. They assimilate carbon from carbon dioxide using the transaldolase variant of the Calvin-Benson-Bassham cycle . The genus comprises motile, rod-shaped cells that can be isolated from low pH environments including low pH microenvironments on otherwise neutral mineral grains. 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

1073-558: The genes that support the survival of these bacteria in acidic environments are presumed to have been obtained by horizontal gene transfer . Acidithiobacillus are chemolithoautotrophs that can occur as acidophilic , mesophilic , or mesothermophilic. Acidithiobacillus caldus can also grow mixotrophically. Currently, the genus comprises ten species which are capable of obtaining energy by oxidizing sulfur compounds, with certain species also utilizing both ferrous and ferric iron. Some species have also evolved to use hydrogen and nitrogen from

1110-438: The genus Thiobacillus prior to 2000, when it was reclassified along with a number of other bacterial species into one of three new genera that better categorize sulfur-oxidizing acidophiles . As a member of the Gammaproteobacteria class of Pseudomonadota , A. caldus may be identified as a Gram-negative bacterium that is frequently found in pairs. Considered to be one of the most common microbes involved in biomining , it

1147-773: The genus, but host microbial communities in which Acidithiobacillus are sometimes present. Optimum pH conditions for these bacteria vary among species, but some have been observed at the genus level in pH conditions as high as 8.94 and temperatures as high as 97.6°C. All species of Acidithiobacillus can grow under pH and temperature conditions between 0.5 to 6.0, and 5°C to 52°C. They are highly tolerant of heavy metals and can flourish in environments where high concentrations of these metals are present. To obtain energy, they have evolved to couple sulfur oxidation to molecular oxygen but can also use other resources around them as electron donors or acceptors. They have adapted to living in these environments through horizontal gene transfer , but

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1184-466: The metabolism of A. caldus are elemental sulfur (S ) and tetrathionate. The hydrolysis of tetrathionate by the key enzyme tetrathionate hydrolase (tetH), composed of 503 amino acids, yields pentathionate, thiosulfate , and sulfur, while elemental sulfur is oxidized by sulfite into sulfate. Most of what is known about the genus Acidithiobacillus comes from experimentation and genomic analyses of two of its species: A. ferrooxidans and A. caldus . With

1221-463: The process of hydrometallurgy. The usage of microorganisms can be used for recovery and extraction of metals. Biohydrometallurgy is used to perform processes involving metals , for example, microbial mining , oil recovery , bioleaching , water-treatment and others. Biohydrometallurgy is mainly used to recover certain metals from sulfide ores . It is usually utilized when conventional mining procedures are too expensive or ineffective in recovering

1258-401: The shape of these microorganisms, which are small rods. The species name, caldus , is derived from the Latin word for warm or hot, denoting this species' love of a warm environment. Thiobacillus caldus was reclassified into Acidithiobacillus , one of three new genera (also including Halothiobacillus and Thermithiobacillus ) created to further classify members of the genus which fall into

1295-407: The sulfide mineral surrounding the desired metal is oxidized to expose the metal of interest, and bioleaching , where the sulfide mineral is solubilized to obtain the metal of interest. Due to the exothermic nature of bioleaching , the thermophilic nature of A. caldus allows for less cooling and quicker rates of bioleaching overall. Bacteria belonging to the genus Acidithiobacillus possess

1332-424: The usual species present, although it is occasionally absent from such locations. 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

1369-577: Was the first acidophilic species of thermophilic thiobacilli to be described. The type strain of this species, DSM 8584, also known as strain KU, has been deposited in the Deutsche Sammlung von Mikroorganismen und Zellkulturen , a collection of microorganisms in Germany. A. caldus is a short, rod -shaped, Gram-negative bacterium that possesses motility via a single polar flagellum located on its outer cell wall, which displays characteristics of

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