Molecular and atomic analysis of the uranium complexes formed by the three eco-types of Acidithiobacillus ferrooxidans

Over 40 years, the intensive uranium mining and milling in the Southeast of Germany (Saxony and Thuringia) has caused environmental pollution in this region. Therefore, it is becoming increasingly clear that such contaminated sites will require a long-term stewardship in addition to remediation. Effective remediation and stewardship will require a better understanding of uranium environmental chemistry. Microbial cells are known to reduce, oxidize, biosorb, bioaccumulate, and bioprecipitate uranium and other actinides. Recently, three different eco-types of A. ferrooxidans were recovered from different sites and depths of two uranium mining wastes. The strains of these three types possess different capability to accumulate and tolerate uranium. In this study, we used a combination of Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy, Time-resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray (EDX) analysis to conduct atomic and molecular scale studies on U(VI) interactions with the three eco-types of A. ferrooxidans. On the basis of the combined information obtained by the above mentioned methods we conclude that the uranium is bound by the cells of the three A. ferrooxidans types in a form of organic uranyl phosphate complexes, which differ in their strength.