Complexation of U(VI) with cells of Thiobacillus ferrooxidans and Thiomonas cuprina of different geological origin

Recently, we demonstrated that the strain Thiobacillus ferrooxidans ATCC 33 020 which is recovered from a uranium mine is taxonomically neither closely related to the type strain of the species Thiobacillus ferrooxidans nor to several other strains of this species stemming from copper and coal mines. In the present work, the interaction was studied of the above-mentioned st rains with U(VI). We found that the uranium mine isolate 33020 accumulates significantly higher amounts of U(VI) in comparison to the other T. ferroox idans strains studied. Extraction studies with sulfuric acid released none, and with EDTA only a small fraction (10-42%) of the U(VI) that was accumul ated by the bacteria. The main part of the uranium was irreversibly bound t o the biomass. Time-resolved laser fluorescence spectroscopy demonstrated t he formation of strong inner-sphere complexes of U(VI) with the bacteria, M oreover, the binding strength of the Thiobacillus ferrooxidans complexes co rresponds to the accumulation capability of the strains, i.e., the stronges t was the complex with the uranium mine isolate 33020. In addition, the interaction was investigated with U(VI) of a bacterial str ain recovered from a uranium mine, but belonging to another bacterial speci es, Thiomonas cuprina. This strain interacts in a different manner with ura nium. Its capability to bind U(VI) was higher than those of all T. ferrooxi dans strains, but the complexes formed were less stable.