Interactions of rare earth elements with bacteria and organic ligands

Ozaki, Takuo; Suzuki, Yoshinori*; Nankawa, Takuya ; Yoshida, Takahiro; Onuki, Toshihiko; Kimura, Takaumi ; Francis, A. J.*

We investigated the interactions of Eu(III) with the common soil bacterium Pseudomonas fluorescens and organic ligands, such as malic acid, citric acid, and a siderophore (DFO). Malic acid formed complexes with Eu(III), but degradation of malic acid was observed when the ratio of malic acid to Eu(III) was high. Citric acid formed a stoichiometric complex with Eu(III) that was not degraded by P. fluorescens. Adsorption of Eu(III) from the DFO complex occurred as a free ion dissociated from DFO and not as the Eu(III)-DFO complex. Time-resolved laser-induced fluorescence spectroscopy analysis showed that adsorption of Eu(III) on P. fluorescens was through a multidentate and predominantly inner-spherical coordination.