Interaction mechanisms of uranium with bacterial strains isolated from extreme habitats


Interaction mechanisms of uranium with bacterial strains isolated from extreme habitats

Merroun, M.; Nedelkova, M.; Heilig, M.; Rossberg, A.; Hennig, C.; Scheinost, A.; Selenska-Pobell, S.

Development of biological methods for removal of heavy metals and actinides are a subject of a great interest due to their low cost and high efficiency at moderate metal concentrations. Many bacterial strains have been isolated that sorb actinides usually at the cell surface. In this paper we describe the isolation of bacterial strains from extreme habitats (such as uranium mining wastes and Siberian deep-well radioactive disposal sites). Phylogenetic analysis of these strains revealed that they are related to α-Proteobacteria and to Actinobacteria. Some of these strains possess the ability to accumulate and tolerate uranium and other heavy metals. Thus, a strain of Microbacterium oxydans (SW3) which was isolated from a uranium contaminated water sample tolerates a concentration of U up to 4 mM and accumulates high amounts (up to 110 mg U/dry biomass at pH 4.5 and an initial uranium concentration of 0.25 mM). X-ray absorption near-edge structure analysis showed that the cells of these strains precipitate U(VI) as autunite-like phase (inorganic uranyl phosphate) at pH 4.5, probably due to the release of inorganic phosphate from the cells. However, at pH 2 uranium formed complexes with organically bound phosphate of the cell surface. At pH 3, both organic and inorganic phosphate uranyl species occur together. We applied Iterative Target Test Factor Analysis /1/ to determine the speciation at different pH values quantitatively from the EXAFS spectra. Transmission electron microscopy and energy dispersive X-ray analysis revealed strain-specific extracellular and/or intracellular uranium accumulations to varying degrees.

References:

/1/ Rossberg, A. et al. 2004. Anal. Bioanal. Chem. 376:631

  • Lecture (Conference)
    Actinides 2005, 04.-08.07.2005, Manchester, Great Britain
  • Contribution to proceedings
    Actinides 2005, Advances in Actinide Science, 04.-08.07.2005, Manchester, Great Britain
    Recent Advances in Actinide Science, Editors: May, I., Alvares, R., Bryan, N.: The Royal Society of Chemistry 2006, 0-85404-678-X, 47-49

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Publ.-Id: 6992