TEM Investigation of U~(6+) and Re~(7+) Reduction by Desulfovibrio desulfuricans, a Sulfate-Reducing Bacterium

摘要

Uranium and its fission product Tc in aerobic environment will be in the forms of UO_2~(2+) and TcO_4~-. Reduced forms of tetravalent U and Tc are sparingly soluble. As determined by transmission electron microscopy, the reduction of uranyl acetate by immobilized cells of Desulfovibrio desulfuricans results in the production of black uraninite nanocrystals precipitated outside the cell. Some nanocrystals are associated with outer membranes of the cells as revealed from cross sections of these metabolic active sulfate-reducing bacteria. The nanocrystals have an average diameter of 5 nm and have anhedral shape. The reduction of Re~(7+) by cells of Desulfovibrio desulfuricans is fast in the media containing H_2 electron donor, and slow in the media containing lactic acid. It is proposed that cytochrome in these cells has an important role in the reduction of uranyl and Re~(7+) that is a chemiical analogue for one uranium fission product Tc~(7+) through transferring electron from molecular hydrogen or lactic acid to the oxyions of UO_2~(2=) and ReO_4~-.