BACTERIAL STRAINS ISOLATED FROM URANIUM MINING WASTE PILES AND THEIR INTERACTIONS WITH URANIUM

Uranium mining waste pile environments are rich in uranium and heavy metals. In addition, they are a reservoir of a large variety of metal-resistant microorganisms. These natural microbial populations are able to influence dissolution and/or precipitation of actinides. The overall goals of this work are to identify the key interactions between uranium and the strains JG-2 and JG-7B isolated from a uranium mining waste pile situated near the town of Johanngeorgenstadt in the Southeast of Germany. Phylogenetic analysis of these strains revealed that they are related to Stenotrophomonas maltophilia and Bacillus sphaericus. As estimated by using ICP-MS these natural isolates possess high ability to accumulate uranium and other heavy metals such as Cd, Pb, Ni and Ag. The Extended X-ray Absorption Fine Structure (EXAFS) analysis of the uranium complexes formed by these isolates demonstrated that the U(VI) is coordinated to phosphate groups in a monodentate fashion with an average distance between the U atom and the P atom of 3.59 ± 0.02 Å. Transmission Electron Microscope (TEM) and Enery-Dispersive X-ray (EDX) analysis demonstrated that the uranium accumulated by S. maltophilia JG-2 is located at the cell wall and in the cytoplasm. In the case of B. sphaericus JG-7B the uranium was located only in the cell wall. In addition, we applied TRLFS in order to determine the energy and the shape of the emission bands and the fluorescence lifetime of the uranium complexes formed by the two different bacterial strains studied in this work. The results may ultimately help to develop effective methods for remediation of heavy-metal-polluted environments.
This work was supported by grant No.03I4004B from the Bundesministerium für Bildung und Forschung, Germany.