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

gram-negative Gram-negative bacteria are bacteria that, unlike gram-positive bacteria, do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. Their defining characteristic is that their cell envelope consists ...

rod-shaped Bacterial cellular morphologies are the shapes that are characteristic of various types of bacteria and often key to their identification. Their direct examination under a light microscope enables the classification of these bacteria (and archae ...

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 (about 99 °F). The term is mainly applied ...

, and

motile Motility is the ability of an organism to move independently using metabolic energy. This biological concept encompasses movement at various levels, from whole organisms to cells and subcellular components. Motility is observed in animals, mi ...

bacterium from the genus of ''

Geobacter ''Geobacter'' is a genus of bacteria. ''Geobacter'' species use anaerobic respiration to alter the redox state of minerals and many pollutants, a trait that makes them useful in bioremediation. ''Geobacter'' was the first organism described wit ...

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

iron Iron is a chemical element; it has symbol Fe () 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, forming much of Earth's o ...

and

uranium Uranium is a chemical element; it has chemical symbol, 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. Ura ...

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

and

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

. It is being studied for use in

bioremediation Bioremediation broadly refers to any process wherein a biological system (typically bacteria, microalgae, fungi in mycoremediation, and plants in phytoremediation), living or dead, is employed for removing environmental pollutants from air, wate ...

projects due to its ability to reduce uranium and

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

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 (; : flagella) (Latin for 'whip' or 'scourge') is a hair-like appendage that protrudes from certain plant and animal sperm cells, from fungal spores ( zoospores), and from a wide range of microorganisms to provide motility. Many pr ...

, 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 a neuron, synaptic vesicles (or neurotransmitter vesicles) s ...

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. Electron acceptors are oxidizing agents. The electron accepting power of an electron acceptor is measured by its redox potential. In the ...

, 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 ...

and

ethanol Ethanol (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...

electron donors The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up and down quarks. El ...

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, and/or radioactive substances. This may be achieved by chemical reaction, dis ...

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

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