Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) research laboratory in Germany have investigated a microorganism capable of transforming water-soluble hexavalent uranium [U(VI)] to the less-mobile tetravalent uranium [U(IV)]. The researchers found that the sulfate-reducing bacterium Desulfosporosinus hippei, a relative of naturally occurring microorganisms present in clay rock and bentonite, showed a relatively fast removal of uranium from clay pore water.