Bio-mineralization of heavy elements on microbial cell surface

微生物細胞での重元素のバイオミネラリゼーション

大貫 敏彦; 田中 万也  ; Jiang, M.; 香西 直文   ; 坂本 文徳  ; 鈴木 義規*; 宇都宮 聡*

Onuki, Toshihiko; Tanaka, Kazuya; Jiang, M.; Kozai, Naofumi; Sakamoto, Fuminori; Suzuki, Yoshinori*; Utsunomiya, Satoshi*

微生物細胞表面における重元素の鉱物化について実験により検討した。ここでは、酵母表面における希土類元素が細胞内より排出されたリン酸と細胞表面で結合し、ナノサイズのリン酸塩鉱物化する現象を見いだした。さらに、生物起源のMn酸化物へのREEsの濃集を調べた結果、Ceにおける濃集異常が低いpHでは正の異常が、高いpHでは負の異常が生じることを明らかにした。この原因が、微生物から排出される有機物であることを突き止めた。

The interaction of heavy elements involving actinides with microorganisms has been studied by experiments. Here, we report the nanoscale mineralization process of REE phosphate on microbial cell surfaces and sorption of REE by biogenic Mn oxide. We found that dissolved Ce was accumulated on the cell surface, and precipitated as nanoscale phosphate mineral, even though no P was added in the solution. The analyses of nanoscale phosphate mineral indicate that the sorbed Ce on the cell surfaces reacted with P released from inside the yeast cell, resulting in the formation of Ce(III) phosphate nanocrystallites of monazite. The biogenic Mn oxide (plus microbial cells) showed large a positive Ce anomaly in acid solution. With increasing pH, the positive Ce anomaly became less pronounced. Furthermore, negative Ce anomalies were observed at a pH of more than 6.5. This anomaly change was caused by organic matters released by bacteria.