Role of fungi in the biogeochemical fate of depleted uranium

Division of Molecular and Environmental Microbiology, College of Life Sciences, University of Dundee, Dundee, Scotland, UK.
Current Biology (Impact Factor: 9.92). 06/2008; 18(9):R375-7. DOI: 10.1016/j.cub.2008.03.011
Source: PubMed

ABSTRACT The testing of depleted uranium (DU; a 97.25% U:0.75% Ti alloy) ammunition and its use in recent war campaigns in Iraq (1991 and 2003) and the Balkans (1995 and 1999) has led to dispersion of thermodynamically unstable DU metal into the environment [1-3]. Although less radioactive, DU has the same chemotoxicity as natural uranium and poses a threat to human populations [1]. Uranium tends to form stable aqueous complexes and precipitates with organic ligands [4], suggesting that living organisms could play an important role in geochemical transformations and cycling. Fungi are one of the most biogeochemically active components of the soil microbiota [5], particularly in the aerobic plant-root zone. Although the mutualistic symbiotic associations (mycorrhizas) of fungi with plants are particularly important in mineral transformations [5], fungal effects on metallic DU have not been studied. Here, we report that free-living and plant symbiotic (mycorrhizal) fungi can colonize DU surfaces and transform metallic DU into uranyl phosphate minerals.

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    • "The hyphae were found to be encrusted with uranium precipitates associated with phosphorus and some fungal species caused the biomineralization of uranyl phosphate minerals of the meta-autunite group. A similar ability of fungi has been demonstrated also in metallic depleted uranium (Fomina et al. 2008). As suggested by Fomina et al. (2007, 2008), the fact that fungi are able to solubilize uranium solids indicates their possible role in biogeochemical cycling of U in the environment. "
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    • "Reductive transformations, nanoparticle formation and nano-biotechnology Microbial activities in anaerobic, subsurface environments also offer possibilities for metal and radionuclide bioremediation (Lloyd, 2003; Lloyd et al., 2003; Lloyd & Renshaw, 2005). Metal(loid)s that form insoluble precipitates when reduced include Se(0), Cr(III), Tc(IV) and U(IV) (Lovley & Coates, 1997; Stolz & Oremland, 1999; Thompson-Eagle & Frankenberger, 1992; Hockin & Gadd, 2003, 2006; Wall & Krumholz, 2006; Yee & Kobayashi, 2008). Microbial reduction of U(VI) to U(IV) has been proposed as a bioremediation strategy for uraniumcontaminated groundwaters (Lovley et al., 1991; Lovley, 1995; Lloyd et al., 2003), as reduction of U(VI) under anaerobic conditions produces U(IV), which precipitates as the insoluble mineral uraninite (Wall & Krumholz, 2006). "
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