Interaction of U(VI) with Bacterial Isolates from Äspö and Mont Terri

Microorganisms are ubiquitous in nature, having a significant impact on the sorption and hence the migration behavior of actinides. Thus it is necessity to characterize the actinide-bacteria species formed and to elucidate the involved interaction mechanisms. This talk deals with the interaction of two microbial strains isolated from destined host rocks for future nuclear waste deposition, namely Pseudomonas fluorescens from Äspö, Sweden, and a novel strain of the genus Paenibacillus from Mont Terri, Switzerland. Potentiometric titration, TRLFS and EXAFS results on the U(VI) interaction with these strains are presented. The talk involves a special focus on the effect of the cell wall constitution (Gram-negative vs. Gram-positive) and the oxygen availability on the U(VI) speciation.