Bacteria Convert Toxic Dissolved Uranium into Rare Stable Compound FeU(V)O₄, Paving Way for Microbial Nuclear Waste Remediation

Researchers studying microorganisms naturally living in a flooded uranium mine in the Ore Mountains have uncovered an unexpected biological mechanism that could help address one of the most persistent challenges in nuclear waste management. The bacteria do not merely absorb dissolved uranium from water; they actively convert it into a rare and chemically stable compound previously thought to form only under very specific geological conditions.

The experiments were conducted using real mine water containing dissolved uranium under strictly anaerobic conditions that replicate the oxygen-free environment found at depths of approximately 2 km. When the scientists added glycerol — a widely available compound found in plant and animal fats and produced during fungal decomposition of wood — as the sole additional carbon and energy source, the bacterial community began to thrive rapidly.

After 130 days, only about 5% of the original dissolved uranium remained in the water. Initial assumptions that the metal was simply accumulating on bacterial cell surfaces were quickly disproven by detailed microscopic and spectroscopic analyses performed at the European Synchrotron Radiation Facility (ESRF) in France, which allows atomic-level examination of materials.

The results showed that a significant portion of the uranium had been reduced to the uncommon pentavalent state (oxidation state +5). This form is normally unstable and quickly converts to more common +4 or +6 states. In this case, however, the pentavalent uranium reacted with iron and oxygen to form the mineral FeU(V)O₄, a compound first discovered only in 2020 in uranium-contaminated soil in Croatia that had remained stable for over 25 years despite exposure to atmospheric oxygen.

Further tests revealed an even more surprising property: when the bacterial biomass was dried and subsequently exposed to oxygen, the amount of FeU(V)O₄ continued to increase rather than degrade. This indicates that oxygen can, under certain conditions, actually promote the formation and persistence of the stable uranium compound.

The findings open new possibilities for bioremediation — the use of living organisms to clean contaminated environments. Current methods for removing uranium from water and soil are expensive and technically complex. If the microbial process can be harnessed effectively, it may provide a sustainable, low-cost alternative for treating former uranium mining sites and other contaminated areas.

Nevertheless, the researchers emphasize that the work remains at the laboratory stage. Future studies will focus on identifying the specific bacterial species responsible, understanding the underlying biochemical pathways, and testing whether the same transformation can be reliably achieved and controlled under real-world environmental conditions.