Researchers at the Helmholtz Center Dresden-Rosendorf in Germany and the University of Granada have shown for the first time that bacteria are able to convert water-soluble uranium into a stable chemical compound when glycerol is available as a food source.
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Scientists expect the results of this study to contribute to future research on using bacteria to help clean up uranium-contaminated environments
Uranium is a radioactive heavy metal, usually found within soil minerals, but mining and other environmental processes can transform uranium into water-soluble forms, and once it becomes mobile, it spreads in the environment and causes problems due to its toxicity.
Deep underground, bacteria may be able to do something amazing, such as trapping toxic uranium before it spreads. When researchers fed microbes found in uranium-contaminated mine water with glycerin, about 95% of the dissolved uranium disappeared within 130 days, as the bacteria helped convert it into an unusually stable uranium compound, rarely observed before.
“There are bacteria that are able to use uranium, a heavy metal that is toxic to humans,” says Dr. Eveline Krawczyk-Barsch, a scientist in the Terrestrial Microbiology Research Group at the Helmholtz Centre Dresden-Rossendorf and a co-author of the study. “Our group’s research has previously revealed that bacteria can use water-soluble uranium in their metabolic processes when glycerol is available as a food source.”
How do bacteria react to uranium?
Bacteria found in soil and water are essential parts of natural ecosystems, and some species are able to process substances that can be harmful to humans and other living organisms.
Glycerol is also a key component of vegetable and animal fats, as it can be formed naturally, for example, when fungi break down wood.
Uranium accumulation in bacterial cell walls
In this study, the researchers wanted to determine how effectively bacteria reduce the amount of uranium dissolved in water and to identify the chemical forms created during the microbes' processing of uranium.
To investigate this, the researchers collected water from a submerged uranium ore mine. In the laboratory, they added a specific amount of glycerin to the water samples and kept them in an oxygen-free environment to create the natural conditions for the bacterial community already present in the mine water. At a depth of about 2,000 meters, there is usually little or no oxygen in the mine. With the conditions suitable for bacterial growth, the microorganisms began using the glycerin as a food source.
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