One of the world’s largest uranium mining operations, the Wismut GmbH Schlema-Alberoda mine in the former Soviet-controlled East Germany, left a lasting environmental burden after decades of extraction.
However, scientists have discovered that the contaminated water filling the abandoned mine may contain a natural answer to the pollution problem. Microorganisms that have adapted to the harsh radioactive environment appear to be evolving ways to survive by interacting with uranium.
The mine ceased operations in 1990 following German reunification, after which extensive and expensive cleanup efforts began to reduce its environmental impact.
A Radioactive Legacy Beneath the Abandoned Mine
After its closure, groundwater flooded the underground tunnels, creating a reservoir of radioactive water that still requires continuous treatment to prevent contamination from spreading.
Uranium is naturally radioactive, and prolonged exposure—such as through drinking contaminated water—can pose serious health risks to humans, animals, and other forms of life, making effective remediation essential.
Despite the high uranium levels in the mine water, a thriving community of microbes has adapted to survive there. Researchers have recently found that, under specific conditions, these microorganisms can also help stabilize uranium.
A team of microbiologists and resource ecologists from Germany’s Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and Spain’s University of Granada conducted the study, with their findings published in Nature Communications.
“Our previous research showed that bacteria can metabolize dissolved uranium in water when glycerol is available as a food source,” said HZDR microbiologist Evelyn Krawczyk-Bärsch.
Bacteria Transform Toxic Uranium into a Stable Form
“This study is the first to demonstrate that bacteria fed with glycerol as a carbon source can transform toxic dissolved uranium into a stable chemical compound.”
Krawczyk-Bärsch and her colleagues started their research using water samples taken from the entrance of the treatment facility at the Wismut GmbH Schlema-Alberoda mine.
“We aimed to recreate the natural environment of the microbial community already present in the mine water, since at depths of around 2,000 meters, oxygen levels are typically extremely low or completely absent,” explained HZDR microbiologist Antonio Newman-Portela.
When the researchers exposed the bacteria to glycerol, they discovered that the microorganisms transformed uranium into a pentavalent form.
In this state, uranium has an uncommon +5 oxidation level, which alters the way it interacts with other elements and allows it to become more easily trapped in stable mineral structures.
A Rare Uranium State Reveals New Environmental Insights
“Uranium is typically found in either the +4 or +6 valence states. Although uranium with a +5 valence does exist, it is uncommon and usually appears only temporarily. Until now, it was considered an unstable oxidation state,” explained Antonio Newman-Portela.
With the bacteria present, the pentavalent uranium reacts with iron and oxygen, producing a compound known as FeU(V)O₄. Scientists had previously identified this material, but they have not yet given it a widely recognized common name.
However, researchers were unaware that this compound could naturally form in the environment or that bacteria could play a role in its creation.
After 130 days, only about 5% of the uranium that was originally dissolved in the water samples remained, according to Newman-Portela.
The researchers found that the bacteria had not only absorbed uranium into their cell walls, but had also converted a significant amount of it into the rare pentavalent form. This made the uranium more likely to react with other elements and produce FeU(V)O₄, particularly after the samples were dried and exposed to oxygen.
Radioactive uranium pollution remains a worldwide environmental challenge.
A Global Challenge of Uranium Water Contamination
In countries such as the United States, India, Canada, France, South Africa, and Australia, levels of uranium contamination in surface water and groundwater have occasionally surpassed the recommended limit of 0.03 milligrams per liter.
Could bacteria offer a natural approach to reducing this radioactive pollution?
The authors note that “over the past 30 years, scientists have explored bioremediation as an affordable and environmentally friendly alternative to traditional physicochemical water treatment methods.”
“Field experiments using biological approaches have shown significant reductions in uranium levels while preventing the production of secondary waste sludge.”
These findings suggest that bacteria could become valuable partners in efforts to remove nuclear contamination, not only in Germany but potentially in affected regions around the world.
Read the original article on: sciencealert
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