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: 9.57). 06/2008; 18(9):R375-7. DOI: 10.1016/j.cub.2008.03.011
Source: PubMed


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 aerobic corrosion of DU is facilitated by fungal biofilms, which retain moisture on DU surfaces and release low-molecular-weight carboxylic acids, which are strong metal chelators able to move away uranium. In this regard, Fomina et al. (2008) demonstrated the effectiveness of freeliving and plant symbiotic (mycorrhizal) fungi to colonize DU surfaces and transform metallic DU into uranyl phosphate minerals. After working at a UK Ministry of Defence weapons testing range, Oliver et al. (2008b) provided evidence that the DU released into the environment during test-firing operations was more labile and more bioavailable than naturally occurring U in soil. "
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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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    ABSTRACT: Concentrations of uranium, thorium and rare earth elements (REE) in 36 species of ectomycorrhizal (26 samples) and saprobic (25 samples) macrofungi from unpolluted sites with differing bedrock geochemistry were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Analytical results are supported by use of certified reference materials (BCR-670, BCR-667, NIST-1575a) and the reliability of the determination of uranium was verified by epithermal neutron activation analysis (ENAA). It appears that data recently published on these elements are erroneous, in part because of use of an inappropriate analytical method; and in part because of apparent contamination by soil particles resulting in elevated levels of thorium and REE. Macrofungi from unpolluted areas, in general, did not accumulate high levels of the investigated metals. Concentrations of uranium and thorium were generally below 30 and 125μgkg−1 (dry weight), respectively. Concentrations of REE in macrofungi did not exceed 360μgkg−1 (dry weight) and their distribution more or less followed the trend observed in post-Archean shales and loess. KeywordsICP-MS–ENAA–REE–Fungi–Bioaccumulation–Metals
    BioMetals 10/2011; 24(5):837-845. DOI:10.1007/s10534-011-9435-4 · 2.50 Impact Factor
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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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    Microbiology 12/2009; 156(Pt 3):609-43. DOI:10.1099/mic.0.037143-0 · 2.56 Impact Factor
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