U(VI) biomineralization by S. acidocaldarius.

Environments with increased uranium concentrations such as uranium mining and processing sites are of a serious public concern due to the considerable chemical and radiological toxicity of this actinide. The mobility and toxicity of uranium in these environments are strongly influenced by a complex of geo-chemical and biotic factors. Microorganisms present in such habitats can influence the migration behaviour by both, direct enzymatic processes such as oxidation and reduction as well as by indirect processes such as biosorption at the cell surface or a passive uptake inside the cells. In addition, uranium can be immobilized in inorganic mineral phases via microbially generated ligands, like sulfide and phosphate, in a process termed biomineralization. Up to date nothing is known about the role of representatives of the third domain of life, the „Archaea” in the biomineralization process of uranium. The objective of the present work was to investigate the interactions of the archaeal strain S. acidocaldarius DSM 639 with U(VI) and to elucidate, in particular, the possible role of archaea in the biomineralization of this radionuclide. For this purpose we used a combination of wet chemistry, microscopic and spectroscopic analyses.