Bacteria can convert toxic uranium into a stable compound that stays locked in place
Across the world, uranium-contaminated water poses a quiet but persistent threat to human health, moving invisibly through aquifers and ecosystems long after the mines that released it have closed. Researchers at Germany's Helmholtz-Zentrum Dresden-Rossendorf have now found that certain bacteria, when fed glycerol, can pull dissolved uranium from water and lock it into a rare, stable compound — one that endures even in open air. The discovery reframes microorganisms not merely as survivors of toxic environments, but as potential architects of remediation, turning a centuries-old problem of industrial contamination toward a biological answer.
- Dissolved uranium from mining operations moves through water systems as a serious health hazard, and existing cleanup methods struggle to contain it at scale.
- In laboratory conditions mimicking a flooded German uranium mine, bacteria removed 95% of dissolved uranium within 130 days — a result that surprised even the researchers.
- The bacteria didn't just absorb the uranium; they transformed it into a rare pentavalent compound bonded with iron and oxygen, a form so unusual it was only first identified in nature in 2020.
- That compound, FeU(V)O4, has proven stable for over 25 years in contaminated Croatian soil, suggesting the bacterial process creates a genuinely durable solution rather than a temporary fix.
- When dried biomass was exposed to oxygen, the stable compound actually increased — hinting that the transformation continues beyond the bacteria's active role and could be engineered for broader use.
- The critical question now is whether this laboratory phenomenon can be translated to real contaminated sites, where conditions are far less controlled and the stakes are far higher.
Uranium becomes dangerous not when it sits locked in rock, but when mining or groundwater movement dissolves it into a mobile, toxic form that travels through water systems. A research team at Germany's Helmholtz-Zentrum Dresden-Rossendorf set out to understand whether bacteria could meaningfully address this problem — and what they found exceeded expectations.
Drawing water from a flooded uranium mine in Germany's Ore Mountains, the scientists recreated the mine's oxygen-scarce conditions in the laboratory and introduced glycerol to feed the bacterial communities already living in the samples. After 130 days, roughly 95% of the dissolved uranium had been removed. The bacteria had pulled it directly into their cell walls — but the more remarkable finding came from what the uranium had become.
Using advanced spectroscopy at the European Synchrotron Radiation Facility in Grenoble, the team discovered that a significant portion of the uranium had shifted into a rare pentavalent state and bonded with iron and oxygen to form a compound called FeU(V)O4. This substance was only first identified in 2020, in Croatian soil contaminated by depleted uranium ammunition, where it had remained stable for more than 25 years despite exposure to open air. Until now, no one knew how it formed or whether biology was involved.
The German team's experiments provide that answer: bacteria, supplied with glycerol, actively generate this durable compound. In a further twist, exposing dried bacterial biomass to oxygen caused the compound to increase rather than degrade — suggesting the stabilization process continues even after the bacteria's initial work is done. Researchers now face the larger challenge of determining whether this biological mechanism can be scaled and applied to real contaminated landscapes, where it might one day render uranium not merely contained, but chemically harmless.
Uranium sits in soil across the world, usually locked in mineral form and relatively inert. But when mining operations tear open the earth or water seeps through contaminated ground, the metal dissolves into a toxic form that moves through water systems and poses a serious threat to human health. A team of researchers at Germany's Helmholtz-Zentrum Dresden-Rossendorf has discovered that certain bacteria can do something remarkable: they can eat uranium, pull it out of solution, and transform it into a stable compound that stays locked in place even when exposed to air.
The story begins with a simple observation. Scientists knew that some bacteria could metabolically process uranium when they had access to glycerol—a fatty compound produced naturally when fungi break down wood. But the real questions were harder: How much uranium could bacteria actually remove from water? And what chemical forms did the uranium take after the bacteria worked on it? To find out, the research team led by Dr. Antonio M. Newman-Portela gathered water samples from a flooded uranium mine in Germany's Ore Mountains, a site operated by Wismut GmbH. At depths around 2,000 meters, where oxygen is scarce, the researchers recreated those oxygen-free conditions in the laboratory and added glycerol to feed the bacterial communities already present in the mine water.
The results were striking. After 130 days, only about five percent of the dissolved uranium remained in the samples. The bacteria had incorporated the uranium directly into their cell walls, accumulating it in a way that pulled it out of the water column. But the real surprise came when the team used advanced microscopy and spectroscopy—including equipment at the European Synchrotron Radiation Facility in Grenoble, France—to determine exactly what chemical form the uranium had taken. Uranium typically exists in one of two states: with a valency of 4 or 6, meaning it bonds to other atoms in predictable ways. Pentavalent uranium, with a valency of 5, is rare and usually unstable. Yet the researchers found that a surprisingly high proportion of the uranium in their samples had transformed into this unusual pentavalent state.
More intriguingly, the pentavalent uranium had bonded with iron and oxygen to form a compound called FeU(V)O4—a substance so new it doesn't yet have a common name. The compound was first identified in 2020 when scientists analyzed soil samples from uranium-contaminated areas in Croatia, where depleted uranium ammunition had left its mark on the landscape. What made that discovery remarkable was that the compound had remained stable for more than 25 years, even when exposed to atmospheric oxygen. Until now, no one understood how this compound formed in nature or whether bacteria played a role in creating it. The German research team's work provides the answer: bacteria, when supplied with glycerol as a food source, actively generate this stable form.
In further experiments, the team observed something counterintuitive. When they dried the bacterial biomass and exposed it to oxygen, the amount of FeU(V)O4 actually increased. This suggests that the transformation continues even after the bacteria have done their initial work, a process that could be harnessed for environmental benefit. Dr. Evelyn Krawczyk-Bärsch, a scientist in the Terrestrial Microbiology research group and co-author of the study, frames the significance plainly: for the first time, researchers have shown that bacteria can convert toxic dissolved uranium into a stable chemical compound under controlled conditions. The next phase of work will determine whether this process can be scaled up and applied to real contaminated sites, and whether bacteria might become a tool for rendering uranium harmless in the environment.
Citações Notáveis
Our study has revealed for the first time that bacteria supplied with glycerol as a carbon source can convert toxic uranium dissolved in water into a stable chemical compound— Dr. Evelyn Krawczyk-Bärsch, Helmholtz-Zentrum Dresden-Rossendorf
A Conversa do Hearth Outra perspectiva sobre a história
So bacteria are eating uranium. How does that even work biologically?
They're not eating it the way we'd eat food. They're using it as part of their metabolism—breaking it down and incorporating it into their cell structures. It's like they're using uranium as a building material while they consume the glycerol for energy.
And this FeU(V)O4 compound—why does it matter that it's stable?
Because uranium in water is mobile and dangerous. It moves through soil, contaminates groundwater, gets into the food chain. But this compound locks the uranium in place. The researchers found it stayed stable for 25 years even in the open air. That's the remediation dream—make the poison immobile.
The bacteria created something that hadn't been seen before in nature?
Not exactly. Scientists found it in Croatian soil in 2020. But they didn't know how it got there or that bacteria made it. This study shows the mechanism—it's a bacterial process, and it happens reliably under the right conditions.
What are those conditions?
Oxygen-free water, a bacterial community, and glycerol as a food source. In nature, that glycerol comes from decomposing wood. In a mine at 2,000 meters deep, you have all of that. The researchers just recreated it in the lab.
Can they scale this up to actually clean contaminated sites?
That's the open question. They've proven the concept works in controlled conditions. But real contaminated sites are messier—different bacteria, different chemistry, different sources of glycerol. The team is still investigating whether this can become a practical remediation tool.
So this is promising but not yet a solution?
Exactly. It's a discovery that opens a door. They've shown bacteria can do something useful with uranium. Now they need to figure out if they can make it work in the real world.