Bacteria collected from a flooded uranium mine in Germany have been able to remove up to 96% of dissolved uranium from contaminated water within 130 days. The findings, published in Nature Communications in July 2026, are the result of research conducted by the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in collaboration with the University of Granada and Wismut GmbH.
The mine in question is Schlema-Alberoda, in the former East Germany — the largest uranium mining operation in Europe, active between 1946 and 1990, with a total output of 231,000 tonnes destined for the Soviet nuclear programme. Researchers collected water samples from the mine’s treatment facility and replicated underground conditions in the laboratory, sealing bottles without oxygen and keeping them in the dark to simulate the environment at approximately 2,000 metres depth. To stimulate the activity of microorganisms already present in the water, glycerol was added as a carbon source. On day one, the water was yellowish. By day 130, a black precipitate had formed at the bottom and the water above had turned clear.
The most striking discovery concerns the chemical form taken by the uranium. The element typically occurs in oxidation states of +4 or +6. The bacteria, however, converted it into pentavalent uranium — a +5 oxidation state considered rare and previously observed only under unstable conditions. In the presence of iron and oxygen, the pentavalent uranium then formed the compound FeU(V)O₄, solid nanoparticles that deposit on the bacterial cell walls. This compound is not entirely unknown — it was first identified in 2020 through analysis of Croatian soils contaminated by uranium munitions — but has yet to receive a common name. Its most significant property is its stability: it remains intact even after exposure to oxygen, unlike many other products of uranium bioremediation.
Conventional treatment methods for uranium-contaminated water are costly and generate hazardous secondary waste. The microbial process described in the study produces no additional byproducts: uranium is simply immobilized within mineral structures inside the bacterial cells. Bioremediation has been studied for three decades as a cost-effective alternative, but the formation of such a stable pentavalent compound had never previously been observed under real mine-water conditions. This pushes the boundaries of what was thought achievable through biological mechanisms alone.
Uranium contamination affects groundwater in many parts of the world: the United States, Canada, Australia, India, South Africa and France have all recorded concentrations exceeding the safety threshold of 0.03 milligrams per litre. The research team sees real potential for adapting this approach to different geographical contexts, adjusting bacterial stimulation conditions based on the local chemical composition of the water. If validated at larger scale, the technique could complement or replace the pump-and-treat chemical systems currently used at decommissioned mining sites, cutting both operational costs and the volume of waste generated.
