Naturally occurring bacteria found in flooded uranium mines can immobilize dissolved uranium by converting it into a stable, solid mineral form. According to research published in Nature Communications by scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Wismut GmbH, and the University of Granada, microbes can remove nearly 95% of dissolved uranium from mine water when provided with glycerol as a metabolic energy source.
How Bacteria Immobilize Uranium
Uranium contamination presents a significant environmental challenge because the metal’s mobility depends on its chemical state. In its dissolved form, uranium spreads easily through groundwater, potentially migrating far from original mine sites. However, when uranium is locked into solid minerals, its movement is restricted.
The research team, led by Antonio M. Newman-Portela, recreated deep-mine conditions in a laboratory using water from a flooded uranium mine in the Ore Mountains. By introducing glycerol to the samples under oxygen-free conditions, the researchers stimulated the native bacterial community. Over a 130-day period, the microbes processed the uranium, converting it into a persistent solid compound within their cell walls.
Did you know?
The bacteria identified in the study do not just store the uranium; they fundamentally change its oxidation state. The researchers discovered an unusually high proportion of pentavalent uranium, a rare and typically short-lived form, stabilized within the bacterial biomass.
The Role of Pentavalent Uranium
The study identified the resulting solid as FeU(V)O4, a compound formed by the combination of uranium, iron, and oxygen. Dr. Evelyn Krawczyk-Bärsch, a co-author from HZDR’s Terrestrial Microbiology group, notes that while this compound was previously observed in soil samples from uranium-contaminated sites in Croatia, its biological origin remained unknown until now.
Evidence suggests this specific compound is remarkably stable. Data from the Croatian site indicated that FeU(V)O4 remained intact for over 25 years, even when exposed to atmospheric oxygen. The HZDR team’s experiments revealed that the addition of oxygen to dried bacterial biomass actually supported the further formation of this compound rather than causing it to degrade.
Future Directions for Bioremediation
While these laboratory results are promising, researchers emphasize that the process is not yet ready for practical cleanup projects. The next phase of research will focus on the practical application of these microbes in real-world settings. Scientists must determine how environmental changes might affect the compound over time.
Current research efforts at HZDR are directed toward uranium-binding bacteria and the biochemical and geochemical reactions that allow the microbes to immobilize the metal. By understanding the precise geochemical reactions occurring at the cell wall, the team hopes to develop more efficient bioremediation strategies for managing uranium-contaminated groundwater and industrial waste sites.
Frequently Asked Questions
- Can these bacteria clean up all uranium contamination?
The current study confirms the process works in controlled laboratory settings using mine water. Further research is required to determine how reliably the process works outside the laboratory. - Is the uranium-based compound harmful?
The goal of this process is to immobilize uranium. By converting it into a stable, solid mineral (FeU(V)O4), the researchers aim to prevent the metal from dissolving into groundwater where it could pose a risk to human health. - Why is glycerol used in this process?
Glycerol serves as a carbon and energy source that stimulates the metabolic activity of the specific bacteria found in the mine water, enabling them to process the heavy metal.
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