Geobacter
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Keywords
Electron Donor Electron Acceptor Aromatic Compound Type Species Ferric IronDefinition
Geobacter is the name of a genus that is located within the Deltaproteobacteria comprising several species of Fe(III)-reducing bacteria (Lovley et al., 1993). The genus Geobacter represents the type genus of the family Geobacteraceae which includes also the genera Desulfuromonas, Desulfuromusa, Geoalkalibacter, Geopsychrobacter, Geothermobacter, Malonomonas, and Pelobacter.
The type species of the genus Geobacter is Geobacter metallireducens strain GS-15, which was enriched and isolated from pristine freshwater sediments of the Potomac River with acetate as the electron donor and poorly crystalline ferric iron as the electron acceptor. In addition to pristine aquatic habitats, Geobacter species were isolated from deep aquifer sediments (e.g., G. chapellei), subsurface sediments (e.g., G. bemidjiensis), or various contaminated sites (e.g., G. sulfurreducens). Cells of Geobacter species stain Gram-negative and are non-spore-forming. All Geobacter species have midrange temperature optima (25–35°C) and grow only under strictly anoxic conditions. Alternative electron acceptors for Geobacter species include nitrate, elemental sulfur, fumarate, malate, Mn(IV), U(VI), Co(III), anthraquinone-2,6-disulfonic acid, and humics. Furthermore, G. metallireducens, G. psychrophilus, and G. sulfurreducens were shown to transfer electrons from the oxidation of organic compounds onto the surface of electrodes. All Geobacter species utilize acetate as electron donor and carbon source; other electron donors that are utilized by the majority of Geobacter species include ethanol, pyruvate, lactate, hydrogen, and formate. Geobacter species are unable to grow by fermentation. Ecological studies indicate that Geobacter species predominate under iron-reducing conditions. Furthermore, the combination of ecological and physiological studies implies that Geobacter species might play important roles in bioremediation processes such as the oxidation of aromatic compounds, the reduction of tetrachloroethene, or the immobilization of U(VI).
Species: G. argillaceus, G. bemidjiensis, G. bremensis, G. chapellei, G. grbiciae, G. humireducens, G. hydrogenophilus, G. lovleyi, G. metallireducens, G. pelophilus, G. pickeringii, G. psychrophilus, G. sulfurreducens, G. thiogenes, G. uraniireducens
Among the validly described Geobacter species, G. metallireducens strain GS-15 and G. sulfurreducens strain PCA are the most intensively studied in terms of physiology, biochemistry, and genetics. The genomes of both species were sequenced and a genetic system was established for G. sulfurreducens (Methé et al., 2003).
Cross-references
Bibliography
- Lovley, D. R., Giovannoni, S. J., White, D. C., Champine, J. E., Phillips, E. J., Gorby, Y. A., and Goodwin, S., 1993. Geobacter metallireducens gen. nov. sp. nov., a microorganism capable of coupling the complete oxidation of organic compounds to the reduction of iron and other metals. Archives of Microbiology, 159, 336–344.CrossRefGoogle Scholar
- Methé, B. A., Nelson, K. E., Eisen, J. A., Paulsen, I. T., Nelson, W., Heidelberg, J. F., Wu, D., Wu, M., Ward, N., Beanan, M. J., Dodson, R. J., Madupu, R., Brinkac, L. M., Daugherty, S. C., DeBoy, R. T., Durkin, A. S., Gwinn, M., Kolonay, J. F., Sullivan, S. A., Haft, D. H., Selengut, J., Davidsen, T. M., Zafar, N., White, O., Tran, B., Romero, C., Forberger, H. A., Weidman, J., Khouri, H., Feldblyum, T. V., Utterback, T. R., Van Aken, S. E., Lovley, D. R., and Fraser, C. M., 2003. Genome of Geobacter sulfurreducens: metal reduction in subsurface environments. Science, 302, 1967–1969.CrossRefGoogle Scholar