A spectroscopic study on U(VI) biomineralization in cultivated Pseudomonas fluorescens biofilms isolated from granitic aquifers.

The interaction between the Pseudomonas fluorescens biofilm and U(VI) were studied using extended X-ray absorption fine structure spectroscopy (EXAFS), and time-resolved laser fluorescence spectroscopy (TRLFS). In EXAFS studies, the formation of a stable uranyl phosphate mineral, similar to autunite (Ca(UO2)2(PO4)2•2-6H2O) or meta-autunite (Ca(UO2)2(PO4)2•10-12H2O) was observed. This is the first time such a biomineralization process has been observed in P. fluorescens. Biomineralization occurs due to phosphate release from the cellular polyphosphate, likely as a cell's response to the added uranium. It differs significantly from the biosorption process occurring in the planktonic cells of the same strain. TRLFS studies of the uranium-contaminated nutrient medium identified aqueous Ca2UO2(CO3)3 and UO2(CO3)3 4− species, which in contrast to the biomineralization in the P. fluorescens biofilm, may contribute to the transport and migration of U(VI). The ob- tained results reveal that biofilms of P. fluorescens may play an important role in predicting the transport behavior of ura- nium in the environment. They will also contribute to the improvement of remediation methods in uranium- contaminated sites.