Within 130 days, bacteria reduce 95% of dissolved uranium and convert it into a stable chemical compound. This has been demonstrated for the first time by a team at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), working in collaboration with Wismut GmbH and the University of Granada. The findings were published in Nature Communications in 2026.
The experiment used water drawn from the flooded Schlema-Alberoda mine in the Saxon Ore Mountains, a site known for particularly high uranium concentrations. The researchers added glycerol to the mine water as a nutrient source for bacteria and monitored the process under anoxic conditions over 130 days. The outcome was clear-cut: only 5% of the originally dissolved uranium remained in free form in the samples. The indigenous bacterial community, stimulated by the glycerol, reduced the uranium and incorporated it into their cell walls. Bacteria belonging to the family Propionibacteriaceae, along with genera such as Berkelbacteria and Propionivibrio, emerged as key players in this metabolic process.
The most unexpected finding concerned the chemical form taken by the uranium. Uranium normally exists with a valence of 4 or 6. Pentavalent uranium — with a valence of 5 — has always been regarded as unstable, a fleeting transitional state. The study, however, detected an unusually high proportion of pentavalent uranium in the analysed biomass, stabilised within the compound FeU(V)O₄ together with iron and oxygen. This compound remained stable for at least 130 days under anoxic conditions and for four weeks even after exposure to oxygen. To precisely characterise the chemical species present, the team employed advanced spectroscopic and microscopic techniques, including experiments conducted at the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility (ESRF) in Grenoble.
The context driving this research is straightforward: mining operations can release uranium from rock and convert it into soluble forms that migrate into groundwater. Once dissolved, uranium is toxic both chemically and due to its radioactivity. Conventional treatment technologies require costly infrastructure and continuous intervention. The prospect of harnessing bacterial communities already present in mine water — simply by stimulating them with a substrate such as glycerol — offers a far more direct approach. Earlier studies had already identified glycerol as an effective electron donor for uranium-reducing bacteria, but none had yet documented the stable formation of pentavalent uranium in a real mine water system.
The implications for the remediation of uranium-contaminated sites are tangible. The researchers stress that understanding the persistence of pentavalent uranium under real environmental conditions is essential for designing more reliable clean-up strategies. Uranium immobilised within bacterial cell walls and converted into insoluble forms does not disperse into the surrounding aquatic environment. If the process is confirmed at larger scale, it could complement or partially replace the chemical treatment plants currently operating at decommissioned mining sites in Germany, the Czech Republic, and other European regions carrying a significant legacy of twentieth-century uranium extraction.
A critical question will be how reproducible these conditions prove to be in aquifers with different geochemical characteristics. The stability of the FeU(V)O₄ compound over time, even in the presence of oxygen, is an encouraging sign. Should further research confirm these results across more heterogeneous environments, uranium bioremediation could establish itself as a standard method for recovering contaminated extraction sites, at considerably lower cost and environmental impact than the purely chemical solutions currently available.
