Associations of Eu (III) with Gram-Negative Bacteria, Alcaligenes faecalis, Shewanella putrefaciens, and Paracoccus denitrificans

Abstract

with bacteria in that these elements may be leaked out of radioactive contaminants. In this study, we used Eu(III) because of its informative fluorescence properties. Europium(III) is a good analogue of Am(III) and Cm(III), and a study on the association of Eu(III) with bacteria is of great help in assessing that of Am(III) and Cm(III), whose long half-lives and high-energy αparticle emission can pose high risks to human health. Time-resolved laser-induced fluorescence spectroscopy is a powerful tool to characterize the coordination environment of Eu(III) with regard to the number of water molecules in the inner-sphere of Eu(III) and the strength of its ligand field both in the inner- and outer-sphere. 14 Previously, we used this technique and successfully characterized the association of Eu(III) with biopolymers (cellulose, chitin, and chitosan) and a unicellular alga Chlorella vulgaris. 15, 16 In the present study, we examined the adsorption behavior of Eu(III) on Gram-negative bacteria A. faecalis, S. putrefaciens, and P. denitrificans by a batch method. Using timeresolved laser-induced fluorescence spectroscopy (TRLFS), we examined the coordination environment of Eu(III) adsorbed on them.