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Acidobacteria is a phylum of bacteria. Its members are physiologically diverse and ubiquitous, especially in soils, but are under-represented in culture.
Beggiatoa is a genus of Gammaproteobacteria belonging the order Thiotrichales, in the Proteobacteria phylum. This genus was one of the first bacteria discovered by Russian botanist Sergei Winogradsky. During his research in Anton de Bary’s laboratory of botany in 1887, he found that Beggiatoa oxidized hydrogen sulfide (H2S) as energy source, forming intracellular sulfur droplets, oxygen is the terminal electron acceptor and CO2 is used as carbon source. Winogradsky named it in honor of the Italian doctor and botanist Francesco Secondo Beggiato. Winogradsky referred to this form of metabolism as "inorgoxidation" (oxidation of inorganic compounds), today called chemolithotrophy. These organisms live in sulfur-rich environments such as soil, both marine and freshwater, in the deep sea hydrothermal vents and in polluted marine environments. The finding represented the first discovery of lithotrophy. Two species of Beggiatoa have been formally described: the type species Beggiatoa alba and Beggiatoa leptomitoformis, the latter of which was only published in 2017. This colorless and filamentous bacterium, sometimes in association with other sulfur bacteria (for example the genus Thiothrix), can be arranged in biofilm visible at naked eye formed by very long white filamentous mate, the white color is due to the stored sulfur. Species of Beggiatoa have cells up to 200 µ in diameter and they are one of the largest prokaryotes on Earth.
Geoglobus is a hyperthermophilic member of the Archaeoglobaceae within the Euryarchaeota. It consists of two species, the first, G. ahangari, isolated from the Guaymas Basin hydrothermal system located deep within the Gulf of California. As a hyperthermophile, it grows best at a temperature of 88 °C and cannot grow at temperatures below 65 °C or above 90 °C. It possess an S-layer cell wall and a single flagellum. G. ahangari is an anaerobe, using poorly soluble ferric iron (Fe3+) as a terminal electron acceptor. It can grow either autotrophically using hydrogen gas (H2) or heterotrophically using a large number of organic compounds, including several types of fatty acids, as energy sources. G. ahangari was the first archaeon isolated capable of using hydrogen gas coupled to iron reduction as an energy source and the first anaerobe isolated capable of using long-chain fatty acids as an energy source.
Microbial metabolism is the means by which a microbe obtains the energy and nutrients it needs to live and reproduce. Microbes use many different types of metabolic strategies and species can often be differentiated from each other based on metabolic characteristics. The specific metabolic properties of a microbe are the major factors in determining that microbe's ecological niche, and often allow for that microbe to be useful in industrial processes or responsible for biogeochemical cycles.
Purple acid phosphatases (PAPs) (EC 3.1.3.2) are metalloenzymes that hydrolyse phosphate esters and anhydrides under acidic condition. In their oxidised form, PAPs in solution are purple in colour. This is due to the presence of a dinuclear iron centre, to which a tyrosine residue is connected via a charge transfer. This metallic centre is composed of Fe3+ and M, where M is Fe3+, Zn2+, Mg2+ or Mn2+. The conserved Fe3+ is stabilised in the ferric form, whereas M may undergo reduction. Upon treatment with mild reductants, PAPs are converted to their enzymatically active, pink form. Treatment with strong reducing agents dissociates the metallic ions, and renders the enzyme colourless and inactive.
Cupriavidus necator is a Gram-negative soil bacterium of the class Betaproteobacteria.
The outflow of acidic liquids and other pollutants from mines is often catalysed by acid-loving microorganisms; these are the acidophiles in acid mine drainage.
Desulfobacter hydrogenophilus is a strictly anaerobic sulfate-reducing bacterium. It was isolated and characterized in 1987 by Friedrich Widdel of the University of Konstanz (Germany). Like most sulfate-reducing bacteria (SRB), D. hydrogenophilus is capable of completely oxidizing organic compounds (specifically acetate, pyruvate and ethanol) to CO2, and therefore plays a key role in biomineralization in anaerobic marine environments. However, unlike many SRB, D. hydrogenophilus is a facultative lithoautotroph, and can grow using H2 as an electron donor and CO2 as a carbon source. D. hydrogenophilus is also unique because it is psychrophilic (and has been shown to grow at temperatures as low as 0 °C or 32 °F). It is also diazotrophic, or capable of fixing nitrogen.
Archaeoglobus profundus is a sulphate-reducing archaea. Archaeoglobus can be found in high-temperature oil fields where it may contribute to oil field souring. A. profundus grows lithotrophically, and while it needs acetate and CO2 for biosynthesis it is heterotrophic.
Geothrix fermentans is a rod-shaped, anaerobic bacterium. It is about 0.1 µm in diameter and ranges from 2-3 µm in length. Cell arrangement occurs singly and in chains. Geothrix fermentans can normally be found in aquatic sediments such as in aquifers. As an anaerobic chemoorganotroph, this organism is best known for its ability to use electron acceptors Fe(III), as well as other high potential metals. It also uses a wide range of substrates as electron donors. Research on metal reduction by G. fermentans has contributed to understanding more about the geochemical cycling of metals in the environment.
Shewanella gelidimarina is a species of bacteria, notable for being an Antarctic species with the ability to produce eicosapentaenoic acid. It grows anaerobically by dissimilatory Fe (III) reduction. Its cells are motile and rod shaped. ACAM 456 is its type strain.
Shewanella frigidimarina is a species of bacteria, notable for being an Antarctic species with the ability to produce eicosapentaenoic acid. It grows anaerobically by dissimilatory Fe (III) reduction. Its cells are motile and rod shaped. ACAM 591 is its type strain.
Ferroplasma acidiphilum is an acidophilic, autotrophic, ferrous iron-oxidizing, cell wall-lacking, mesophilic member of the Ferroplasmaceae. F. acidophilum is a mesophile with a temperature optimum of approximately 35 °C, growing optimally at a pH of 1.7. F. acidophilum is generally found in acidic mine tailings, primarily those containing pyrite (FeS2). It is especially abundant in cases of severe acid mine drainage, where other organisms such as Acidithiobacillus and Leptospirillum lower the pH of the environment to the extent that F. acidophilum is allowed to flourish.
Desulfitobacterium chlororespirans is a Gram-positive, anaerobic, spore-forming species of bacteria. Its type strain is Co23. It grows by coupling the oxidation of lactate to the reductive dechlorination of 3-chloro-4-hydroxybenzoate.
Acidithiobacillus caldus formerly belonged to 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 Proteobacteria, 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 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 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.
Pelobacter carbinolicus is a species of bacteria that ferments 2,3-butanediol and acetoin. It is Gram-negative, strictly anaerobic and non-spore-forming. Gra Bd 1 is the type strain. Its genome has been sequenced.
Rhodoferax is a genus of Betaproteobacteria belonging to the purple nonsulfur bacteriarophic. Originally, Rhodoferax species were included in the genus Rhodocyclus as the Rhodocyclus gelatinous-like group. The genus Rhodoferax was first proposed in 1991 to accommodate the taxonomic and phylogenetic discrepancies arising from its inclusion in the genus Rhodocyclus. Rhodoferax currently comprises four described species: R. fermentans, R. antarcticus, R. ferrireducens, and R. saidenbachensis. R. ferrireducens, lacks the typical phototrophic character common to two other Rhodoferax species. This difference has led researchers to propose the creation of a new genus, Albidoferax, to accommodate this divergent species. The genus name was later corrected to Albidiferax. Based on geno- and phenotypical characteristics, A. ferrireducens was reclassified in the genus Rhodoferax in 2014. R. saidenbachensis, a second non-phototrophic species of the genus Rhodoferax was described by Kaden et al. in 2014.
Desulfitobacterium metallireducens is an anaerobic bacterium that couples growth to the reduction of metals and humic acids as well as chlorinated compounds. Its type strain is 853-15A(T). It was first isolated from a uranium-contaminated aquifer sediment.
Geobacter psychrophilus is a Fe(III)-reducing bacterium. It is Gram-negative, slightly curved, rod-shaped and motile via means of monotrichous flagella. Its type strain is P35T.
Acidithrix ferrooxidans is a heterotrophic, acidophilic and Gram-positive bacterium from the genus of Acidithrix. The type strain of this species, A. ferrooxidans Py-F3 was isolated from an acidic stream draining from a copper mine in Wales. This species grows in a variety of acidic environments such as streams, mines or geothermal sites. Mine lakes with a redoxcline support growth with ferrous iron as the electron donor. A. ferrooxidans grows rapidly in macroscopic streamer, producing greater cell densities than other streamer-forming microbes. Use in a bioreactors to remediate mine waste has been proposed due to cell densities and rapid oxidation of ferrous iron oxidation in acidic mine drainage. Exopolysaccharide production during metal substrate metabolism, such as iron oxidation helps to prevent cell encrustation by minerals.
References
- ↑ Harrison, A. P. (1981). "Acidiphilium cryptum gen. nov., sp. nov., Heterotrophic Bacterium From Acidic Mineral Environments". International Journal of Systematic Bacteriology. 31 (3): 327–332. doi: 10.1099/00207713-31-3-327 . ISSN 0020-7713.
