Uranium(VI) accumulation in selected bacterial and fungal cells

Bacteria and fungi in soil, sediment and water may have a significant influence on the transport of radionuclides and other heavy metals in nature. In addition to chemical and physical factors, that affect the migration behaviour of uranium, metabolic processes play an important role in its mobilisation or immobilisation. The aim of this project is to look for possible uranium uptake systems in selected bacteria and fungi, showing high uranium accumulation capacities. In our institute we are using different microscopic, spectroscopic and chromatographic methods for the localization of accumulated uranium and for the identification of binding relevant compounds on the cell surface and inside the cell.
The Arthrobacter strain JG37-Iso2, isolated from a soil sample of a uranium mining waste pile near the town of Johanngeorgenstadt (JG) in Germany, is able to accumulate large amounts of uranium inside the cell. Therefore systematic investigations of the growth behaviour, uranium binding and uranium accumulation of Arthrobacter JG37-Iso2 were performed. As indicated by the TEM analysis, uranium diffuses in the cells during the stationary growth phase, possibly due to a higher permeability caused by damages of the cell membranes. For comparison we also investigate the interaction of uranium(VI) with the reference strains Arthrobacter oxygen and Arthrobacter nicotinae. Both strains show a different binding behaviour for uranium. First spectroscopic results indicate the coordination of uranium via carboxylic groups of the cell compartments, whereas a additional co-ordination to organic phosphate groups can currently not be excluded.