Interactions of heavy elements with microorganisms

重元素と微生物との相互作用

大貫 敏彦; 吉田 崇宏*; 尾崎 卓郎; 坂本 文徳  ; 香西 直文   ; 南川 卓也 ; 鈴木 義規; Francis, A. J.

Onuki, Toshihiko; Yoshida, Takahiro*; Ozaki, Takuo; Sakamoto, Fuminori; Kozai, Naofumi; Nankawa, Takuya; Suzuki, Yoshinori; Francis, A. J.

Pu(IV)の微生物への吸着及び還元,U(VI)の微生物による鉱物化についての成果を紹介する。Pu(IV)-DFO錯体の吸着では配位子交換が主であった。Pu(IV)の一部は硫酸還元菌によりPu(III)に還元した。一方、U(VI)は酵母細胞へ吸着され、一部がウラニルリン酸塩鉱物化した。溶液の化学状態はウラニル鉱物の生成について不飽和であった。鉱物化は細胞表面に吸着したU(VI)と細胞内から漏出したPが反応して、溶液中の化学条件が不飽和にもかかわらず、進行したと考えられた。

We have been conducting basic scientific research on microbial interactions with actinides in order to elucidate the environmental behavior of actinides under relevant microbial process conditions. Adsorption of Pu(IV)-desferrioxamine B (DFO) on bacteria indicate that Pu(IV) is dissociated by contact with cells, after which Pu(IV) is adsorbed. Study on reduction of Pu(IV) in the presence of citric acid at pH 7.0 suggested that Pu(IV) is reduced to Pu(III) by the activity of sulphate reducing bacteria. Analysis of the U(VI)-bearing precipitates by FESEM-EDS, TEM, and visible diffuse reflectance spectrometry demonstrated the presence of H-autunite, HUOPO;4HO and thermodynamic calculations suggest that the chemical compositions of the solutions were undersaturated with respect to H-autunite. The yeast's cell surfaces, rather than the bulk solution, offer the specific conditions for this geochemical process.