A NOVEL PHOSPHORIMAGER-BASED TECHNIQUE FOR MONITORING THE MICROBIAL REDUCTION OF TECHNETIUM

A novel PhosphorImager-based technique which can be used to quantify l ow concentrations of radionuclides is described, The technique offers several benefits, combining very high sensitivity with containment of the radioisotope in the solid state, thus minimizing disposal procedur es. In this study, it was used in conjunction with paper chromatograph y to quantify different oxidation states of Tc-99 in solution. The tec hnique was used to evaluate the potential of anaerobic cultures of She wanella putrefaciens and Geobacter metallireducens (bacteria with know n metal-reducing capabilities) to reduce highly soluble Tc(VII) to ins oluble lower-valence species, facilitating its removal from solution, Both organisms reduced Tc(VII), but profiles of Tc species produced in culture supernatants were strain specific, S, putrefaciens produced T c(V), Tc(IV), and one unidentified species, but no Tc was removed from solution, G. metallireducens removed 70% of the 250 mu M Tc added in solution, with trace amounts of Tc(V) and the unidentified species det ected in culture supernatants. Possible uses for these organisms in th e bioremediation of Tc contaminated waters are discussed, and other us es of the PhosphorImager technique are highlighted.