Laser spectroscopic studies of interactions of U^VI with bacterial phosphate species

We have investigated the interactions of U^VI with two bacterial phosphate-containing species: Gram-positive Bacillus sphaericus and Gram-negative Psedomonas aeruginosa. The Gram-positive B. sphaericus was investigated by using Raman spectroscopy and time-resolved laser-induced fluorescence spectroscopy (TRLFS). We found that living cells, spores, and intact heat-killed cells complexed U^VI (pH4.5) through phosphate groups bound to their surfaces, while decomposed cells released H₂PO₄^- and precipitated U^VI as UO₂(H₂PO₄)₂. TRLFS of U^VI showed that Gram-negative P. aeruginosa - genetically engineered to accumulate polyphosphate, subsequently degrade it, and secrete phosphate - precipitated U^VI quantitatively at pH 4.5, The same bacterial strain, not induced to secrete phosphate, sorbed only a small amount of U^VI.