Fungal transformations of uranium oxides

Abstract

The biogeochemical activities of free-living and symbiotic fungi must be acknowledged in attempts to understand uranium cycling and dispersal in the environment. Although the near-surface geochemistry of uranium is very complex and a wide variety of mineral phases is known, uranium trioxide (UO3) and triuranium octaoxide (U(3)O(8)) can be used as well characterized models in the study of biotransformations. We have used a complex methodological approach involving advanced solid state speciation and scanning electron microscopy to study the ability of saprotrophic, ericoid and ectomycorrhizal fungi to transform these model oxides. This study has revealed that fungi exhibit a high uranium oxide tolerance, and possess the ability to solubilize UO3 and U(3)O(8) and to accumulate uranium within the mycelium to over 80 mg (g dry weight)(-1) biomass. X-ray absorption spectroscopy of uranium speciation within the biomass showed that in most of the fungi the uranyl ion was coordinated to phosphate ligands, but in ectomycorrhizal fungi mixed phosphate/carboxylate coordination was observed. Abundant uranium precipitates associated with phosphorus were found in the mycelium and encrusted the hyphae. Some of the fungi caused the biomineralization of well-crystallized uranyl phosphate minerals of the meta-autunite group. This is the first experimental evidence for fungal transformations of uranium solids and the production of secondary mycogenic uranium minerals.

Effect of heavy metals on cultural and morphological growth characteristics of halotolerant Penicillium morphotypes

“…The change in growth pattern from a loose nature on control medium without metals to a more dense compact growth with narrower colony diameter in presence of Cu 2+ and Cd 2+ was similar to that reported to occur in B. caledonica colonies on media containing lead phosphate and cuprite [9] and uranium oxide [10] although the morphology of Penicillium simplicissimum isolate in presence of uranium oxides did not change significantly [10]. It was observed that resistance to higher concentrations of metals was linked to the production of pigment; this was more noticeable in MP4 which had higher resistance to metals than the other cultures.…”

Metals, minerals and microbes: geomicrobiology and bioremediation

“…Apart from the more detailed biomineral examples that follow, a variety of other secondary minerals have been recorded associated with fungal biomass, e.g. birnessite, ferrihydrite, iron gluconate, calcium formate, forsterite, goethite, halloysite, hydrocerussite, todorokite, moolooite, montmorillonite and uranium phosphates (Burford et al, 2003a, b;Gadd, 2007;Fomina et al, 2007aFomina et al, , b, 2008 (Fig. 4).…”

“…Ferromanganese nodules on parts of the ocean floor are inhabited by manganese-oxidizing and -reducing bacteria, and these are likely to contribute to nodule formation (Ehrlich & Newman, 2009 (Ehrlich & Newman, 2009). Secondary mycogenic uranium mineral precipitates on fungal mycelia growing in the presence of uranium oxides or depleted uranium were found to be uranyl phosphate minerals of the meta-autunite group, uramphite and/or chernikovite (Fomina et al, 2007a(Fomina et al, , 2008 (Fig. 4).…”

Bioaccumulation and biosorption of inorganic nanoparticles: factors affecting the efficiency of nanoparticle mycoextraction by liquid-grown mycelia of Pleurotus eryngii and Trametes versicolor

“…It was documented that macrofungi are effective accumulators of silver (Borovicka et al 2010). Among others, fungi have been shown to biomineralize uranium oxides, suggesting that they may have application in the bioremediation of radioactively polluted sites (Fomina et al 2007(Fomina et al , 2008. One of such fungi is Pleurotus eryngii, analyzed in our laboratory, which accumulates cesium in the fruitbody Bazała et al 2005Bazała et al , 2008 and in biotechnologically cultivated mycelium.…”