Microbial Bioremediation of Uranium

Microorganisms immobilize uranium from contaminated environments by transforming it into less soluble forms through mechanisms such as bioreduction, biosorption, bioaccumulation, and biomineralization.

Hexavalent uranium is water-soluble, which migrates easily through groundwater and contaminates surrounding areas. In bioreduction, microbes such as Geobacter and Shewanella use their c-type cytochromes to convert hexavalent uranium into a tetravalent form.

The tetravalent uranium then precipitates as solid uraninite, reducing its mobility and containing the contamination.

Biosorption involves the passive binding of uranium ions to functional groups such as carboxyl, phosphate, and hydroxyl groups on microbial surfaces, reducing the contamination.

In bioaccumulation, microbes absorb uranium and transport it inside their cells, where it is stored, often bound to polyphosphate granules.

Some microbes, including Microbacterium and Caulobacter, trigger biomineralization by enzymatically releasing phosphate, which reacts with uranium ions to form stable uranium-phosphate minerals.