In water-rock interactions, microbes play an important role in mobilization and immobilization of metals, including radionuclides. Water of three wells from a rhyolite joint aquifer known for high Rn and Ra concentrations were investigated for their microbial communities and hydrochemistry. The saline waters of NaCl type were used to isolate strains of the native microbe population. Both Gram-negative, like
and Gram-positive, e.g.
were identified. These microbes can produce siderophores, necessary to supply the cells with iron. In addition to iron, such small molecules may complex other elements, including radionuclides. Thus, they can impact the mobility of radionuclides in the groundwater. The potential of microbial processes in radionuclide reactive transfer is further discussed with respect to other potential mechanisms.