Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

1 Publication
Effect of pH on the speciation of uranium(VI) associated with bacterial strains isolated from extreme habitats: Spectroscopic and microscopic studies
Merroun, M.; Nedelkova, M.; Rossberg, A.; Hennig, C.; Selenska-Pobell, S.;
This paper deals with the speciation of U(VI) associated with the cells of bacterial strains isolated from extreme habitats as function of pH. For this propose, a combination of synchrotron-based X-ray absorption spectroscopy (XAS), time-resolved laser-induced fluorescence spectroscopy (TRLFS), transmission electron microsocpe (TEM) coupled with energy dispersive-X ray (EDX) analysis and electron diffraction were used. XAS analysis indicated that the effect of pH on the local coordination of U in the U-complexes formed by the different bacterial strains is species specific. No structural differences were found between the U complexes formed by three different exo-types of Acidothiobacillus ferrooxidans at pH 2, 3 and 4.5. In contrast, the cells of Bacillus sphaericus JG-B7, Microbacterium oxydans M2, and Sphingomonas sp. S15-S1 precipitate U(VI) as a meta-autunite-like phase at pH 4.5, probably due to the release of the inorganic phosphate from the cells. At pH 2, the U is coordinated to the organic phosphate groups of the cells of the listed bacteria. Both organic and inorganic uranyl / bacterial complexes were formed at pH 3. TEM/EDX analysis confirm these results and showed strain-specific extracellular and/or intracellular uranium accumulation to varying degrees. We applied Iterative Target Test Factor Analysis to determine the uranium speciation at different pH values quantitatively from the EXAFS spectra. Different hypothesis explaining the different coordination chemistry of uranium to bacteria as a function of pH of uranium solution in terms of solubility of m-autunite and/or microbial activity will be discussed.
  • Lecture (Conference)
    11th International Symposium on Microbial Ecology, ISME-11, 20.-25.08.2006, Vienna, Austria

Publ.-Id: 8356 - Permalink