''Geobacter uraniireducens'' (more recently known as ''Geotalea uraniireducens'') is a

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 wa ...

rod-shaped A bacillus (), also called a bacilliform bacterium or often just a rod (when the context makes the sense clear), is a rod-shaped bacterium or archaeon. Bacilli are found in many different taxonomic groups of bacteria. However, the name '' Bacil ...

anaerobic Anaerobic means "living, active, occurring, or existing in the absence of free oxygen", as opposed to aerobic which means "living, active, or occurring only in the presence of oxygen." Anaerobic may also refer to: *Adhesive#Anaerobic, Anaerobic ad ...

chemolithotrophic

mesophilic A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37°C. The term is mainly applied to microorganisms. Org ...

, and

motile Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms th ...

bacterium from the genus of ''

Geobacter ''Geobacter'' is a genus of bacteria. ''Geobacter'' species are anaerobic respiration bacterial species which have capabilities that make them useful in bioremediation. ''Geobacter'' was found to be the first organism with the ability to oxidiz ...

''. G. ''uraniireducens'' has been found to reduce

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 ...

and

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly ...

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

and

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former ...

. It is being studied for use in

bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi, and plants), living or dead, is employed for removing environmental pollutants from air, water, soil, flue gasses, industrial effluent ...

projects due to its ability to reduce uranium and

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, bu ...

History

''Geobacter uraniireducens'' was isolated from the subsurface sediment of a previous uranium ore processing facility undergoing uranium

in 2002. This occurred during a field study by Robert Anderson and his associates at the Old Rifle in situ test plot area in Rifle, Colorado. Shelobolina et al. (2008) further described the strain Rf4^T While ''Geobacter uraniireducens'' is the

basonym In the scientific name of organisms, basionym or basyonym means the original name on which a new name is based; the author citation of the new name should include the authors of the basionym in parentheses. The term "basionym" is used in both botan ...

, David Waite and associates reclassified it to the current preferred name, ''Geotalea uraniireducens'' in their 2020 paper.

Characteristics

''G. uraniireducens'' are gram negative bacteria that are motile rods with rounded ends and two to four long lateral

flagellum A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

, as well as pili and

vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like feature ...

Extracellular electron transport strategies

The strategy of ''G. uraniireducens'' for extracellular electron transport (EET) is to facilitate iron (Fe(III)) oxide reduction via the production of a soluble electron shuttle. It has been found that riboflavin mediates EET to reduce extracellular electron acceptors. This is important because unlike in most ''Geobacter'' species, where conductive pili are critical for effective reduction of extracellular electron acceptors, the pili of ''G. uraniireducens'' are not conductive.

Metabolic mechanisms

''G. uraniireducens'' is an iron-reducing bacteria that uses acetate as an electron donor and reduces uranium (U(VI)). In addition to Fe(III), it is also able to use Mn(IV), anthraquinone-2,6-disulfonate, malate and fumarate as electron acceptors. As it uses Fe(III) oxide as the

electron acceptor An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process. Electron acceptors are sometimes mist ...

, it can oxidize

acetate An acetate is a salt formed by the combination of acetic acid with a base (e.g. alkaline, earthy, metallic, nonmetallic or radical base). "Acetate" also describes the conjugate base or ion (specifically, the negatively charged ion called ...

, lactate,

pyruvate Pyruvic acid (CH3COCOOH) is the simplest of the alpha-keto acids, with a carboxylic acid and a ketone functional group. Pyruvate, the conjugate base, CH3COCOO−, is an intermediate in several metabolic pathways throughout the cell. Pyruvic aci ...

and

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a h ...

electron donors In chemistry, an electron donor is a chemical entity that donates electrons to another compound. It is a reducing agent that, by virtue of its donating electrons, is itself oxidized in the process. Typical reducing agents undergo permanent ch ...

Applications

Bioremediation

''G. uraniireducens'' have been used in bioremediation studies in situ to

decontaminate Decontamination (sometimes abbreviated as decon, dcon, or decontam) is the process of removing contaminants on an object or area, including chemicals, micro-organisms or radioactive substances. This may be achieved by chemical reaction, disinfect ...

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidat ...

containing high levels of uranium from previous activities. This process can be enhanced by using acetate to stimulate increased populations.

Environmental implications

One environmental implication of interest in ''G. uraniireducens'' is its arsenic (As(V)) reducing capabilities in subsurface sediments. This ability is proposed to be due to gene encoding for respiratory arsenate reductase.

References

External links

Type strain of ''Geobacter uraniireducens'' at Bac''Dive'' - the Bacterial Diversity Metadatabase
Bacteria described in 2008 Thermodesulfobacteriota