Actinides in biological systems
Selected research examples
Microorganisms have developed a variety of strategies to survive even the harsh conditions of uranium mine piles or nuclear waste disposal sites. Alive or dead, they influence the geochemical pathways of actinides by a multitude of chemical reactions. One example is shown on the right, where U is precipitated as the insoluble uranyl phosphate mineral autunite outside of livings cells at the physiologically more favorable pH of 4.5. At lower pH, uranyl is still retained from the cells' interior by sorption to phosphate groups in the cell membrane. Metabolic reactions also strongly influence the redox of actinides, thereby creating a vast variety of chemical species due to the multiple oxidation states of actinoids. The example on the left shows the complex redox reactions of plutonium at the surface of Desulfovibrio äspöensis, a microorganism isolated from a designated nuclear waste repository.
Moll H., Merroun M. L., Hennig C., Rossberg A., Selenska-Pobell S., and Bernhard G. (2006) The interaction of Desulfovibrio äspöensis DSM 10631T with plutonium. Radiochim Acta 94, 815-824. Merroun M., Nedelkova M., Rossberg A., Hennig C., and Selenska-Pobell S. (2006) Interaction mechanisms of bacterial strains isolated from extreme habitats with uranium. Radiochim Acta 94, 723-729. Merroun M. L., Raff J., Rossberg A., Hennig C., Reich T., and Selenska-Pobell S. (2005) Complexation of uranium by cells and S-layer sheets of Bacillus sphaericus JG-A12. Applied and Environmental Microbiology 71, 5532-5543. Merroun M., Hennig C., Rossberg A., Reich T., and Selenska-Pobell S. (2003) Characterization of U(VI)-Acidithiobacillus ferrooxidans complexes using EXAFS, transmission electron microscopy, and energy-dispersive X-ray analysis. Radiochim Acta 91, 583-591.