Interactions between Metals and Bacteria: Fundamental and Applied Research

Soils, sediments, and waters heavily polluted with radionuclides and other toxic metals, are a reservoir of unusual bacteria well adapted to these toxic environments. These bacteria possess fascinating mechanisms for interaction with and bio-transformation of radionuclides and other heavy metals, thus regulating the mobility of the metals in the environment. This paper will give an overview on the different mechanisms of interaction between radionuclides/metals and bacterial strains isolated from different extreme habitats including uranium mining waste piles as well as groundwater of a radioactive repository. For this purpose, a combination of spectroscopic (EXAFS, XANES, TRLFS), microscopic (TEM), microbiological and wet chemistry techniques is used. Elucidating the interaction mechanisms microbe/metals is helpful for understanding the role which bacteria play in the transport and mobility of toxic metals in the environment as well as their biotechnological application in the bioremediation of heavy metal contaminated waters. Another application of the isolated bacterial cells and their biocomponents is in the field of nanotechnology. Thus, the surface layer (S-layer) protein of Bacillus sphaericus JG-A12, a bacterium isolated from a uranium mining waste pile near the town of Johanngeorgenstadt in Germany, is used as template for the formation of noble metal (Pd, Pt, Au, etc.) nanoparticles for industrial application (e.g. catalysis). The structure and the size of these metallic nanoparticles were characterized using synchrotron radiation-based methods such as X-ray absorption spectroscopy.