Bacteria from uranium waste piles and their interactions with uranium (VI)

Gram-positive spore-forming bacterial isolates belonging to the species Bacillus cereus, B. sphaericus and B. megaterium and also Gram-negative chemolithoautotrophic isolates of the species Thiobacillus ferrooxidans and Leptospirillum ferrooxidans were cultured from soil and sediment samples of several uranium polluted waste piles in Saxony, Germany. The interactions of these natural bacterial isolates with uranium (in particular, sorption - desorption, accumulation, reduction, and tolerance) were studied.
We have demonstrated that the natural Bacillus isolates are able to accumulate selectively and reversible a variety of toxic metals from drain waters of a uranium mining waste pile (Selenska-Pobell et al., 1999). By the use of extended X-ray absorption fine structure (EXAFS) analysis and time resolved laser fluorescence spectroscopy (TRLFS) it was demonstrated that the main chemical group involved in the interaction of the mentioned Bacillus strains with U(VI) is the phosphate group (Hennig et al., 1999; Panak et al., 2000).
Our studies on the interactions of the recently described in our laboratory three ecological types (eco-types) of T. ferrooxidans (Selenska-Pobell et al., 1999) and two eco-types of L. ferrooxidans (Tzvetkova et al., 1999) with uranium (VI) by the use of EXAFS, TRLFS, and infrared spectroscopy (IRS) indicate that the nature and the strength of the uranium complexes built by these Gram-negative acidophilic chemolithoauthotrops differ significantly from those built on the cell surfaces of the Gram-positive Bacilli. The tolerance and the interactions of the natural T. ferrooxidans isolates with U were type-specific.