Researchers have engineered a solar-powered bacterial system that removed 94 percent of uranium from contaminated mine wastewater in lab tests, compared with 48 percent for unmodified microbes. The team fused Shewanella putrefaciens bacteria with ferrous sulfide nanoparticles to create a self-repairing biohybrid that harnesses sunlight to convert dissolved uranium into an insoluble form that precipitates out of solution. The researchers describe the approach as a solar-driven alternative to conventional chemical and physical treatment methods for uranium-contaminated water.
How Bacteria and Iron Sulfide Strip Uranium From Water
The core innovation is a living composite: Shewanella putrefaciens cells coated with biogenic ferrous sulfide (FeS) nanoparticles that grow directly on the cell surface. When exposed to light, the FeS acts as a semiconductor antenna, absorbing photons and channeling electrons into the bacterium’s own metabolic machinery. That extra electron flow accelerates the reduction of soluble uranium(VI) to insoluble uranium(IV), which precipitates out of solution and can then be removed from the treated water. A Science Bulletin study detailing this biohybrid system reports that it achieved 94 percent uranium removal when applied to real uranium mine wastewater, compared with just 48 percent for pristine Shewanella putrefaciens cells working alone.
What makes the system particularly practical is its capacity to regenerate. The FeS nanoparticles degrade during operation, but the bacteria continuously biosynthesize fresh nanoparticles in situ, restoring the semiconductor coating without any external intervention. Earlier work on chromium-contaminated wastewater showed that biogenic FeS nanoparticles could be repeatedly renewed by the host organism, allowing multiple treatment cycles without performance collapse. Applying that principle to uranium means the same culture can, in theory, run through extended treatment campaigns without replacement parts or chemical reagents, a significant operational advantage over conventional ion-exchange or chemical precipitation methods that generate secondary waste streams and require frequent media changeouts.
Why the Bacteria’s Own Coating Matters
The biohybrid’s performance depends not only on the FeS semiconductor but also on the sticky organic layer that Shewanella putrefaciens naturally secretes. These extracellular polymeric substances, or EPS, serve as both a scaffold for nanoparticle attachment and a direct participant in uranium capture. Research in Ecotoxicology and Environmental Safety found that stripping EPS from the bacterial surface measurably reduced uranium removal efficiency, confirming that the organic matrix is not a passive bystander. Functional groups within the EPS bind uranium ions and promote surface biomineralization, effectively turning the bacterium into a microscopic uranium trap even before the FeS photoelectron boost kicks in.
A parallel line of research using cadmium sulfide (CdS) instead of FeS as the semiconductor partner offers additional mechanistic insight. In that system, described in an ACS Materials Letters article, Shewanella-based biohybrids achieved greater than 90 percent uranium removal in real mine wastewater and used in situ Kelvin probe force microscopy to directly image photoelectron transfer from the semiconductor to the bacterial cell. Transcriptomic analysis showed that genes involved in electron transport were upregulated under illumination, meaning the bacteria actively adapted their metabolism to exploit the incoming photoelectrons. Together, these findings suggest that Shewanella putrefaciens is not merely a passive host for semiconductor particles but an active partner that tunes its biology to maximize uranium capture when light is available.
Solar Remediation in a Broader Context
The biohybrid approach sits within a growing family of solar-driven water treatment technologies that target heavy metals. A recent peer-reviewed review of solar-based metal removal methods places uranium among the contaminants addressable by photocatalysis, solar distillation, and solar-driven redox processes, while also flagging real-world constraints such as variable sunlight intensity, catalyst fouling, and the gap between laboratory demonstrations and field-scale deployment. Within this landscape, the Shewanella biohybrids represent a hybrid between photocatalysis and bioremediation, using sunlight not only to drive redox reactions directly on a catalyst surface but also to energize a living electron-transfer network.
Purely inorganic photocatalytic systems, for example those exploiting engineered oxygen vacancies and thermoelectric effects for uranium(VI) photoreduction, have shown strong laboratory results with rapid kinetics under controlled illumination. However, these catalysts typically suffer from gradual deactivation, photocorrosion, or surface fouling and must be replaced or chemically regenerated, adding cost and complexity. The bacterial biohybrid sidesteps some of these issues because the living cells continuously rebuild the active FeS material and maintain an extracellular matrix that can trap and immobilize uranium-bearing solids. A separate study on scaled-up semiconductor–biohybrids further indicates that bio-FeS constructs an artificial transmembrane electron channel that facilitates extracellular electron transfer, pointing toward a general platform that could be adapted for other toxic metals in mining effluent beyond uranium alone.
Gaps Between the Lab and the Mine Site
For all its promise, the 94 percent removal figure comes from controlled experiments on real wastewater samples, not from a continuous treatment plant operating at a mine. Several practical questions remain open. Sunlight availability varies by latitude, season, and weather, and the published studies do not yet quantify how performance degrades under low-light or intermittent-light conditions over weeks or months. Reactor design will need to address how to expose dense bacterial suspensions to sufficient light while maintaining mixing and contact with incoming wastewater, and how to handle turbid or particle-rich streams that can strongly attenuate sunlight. The research also lacks head-to-head cost comparisons with established physicochemical treatment methods such as chemical precipitation, membrane filtration, and ion exchange, which are widely used for uranium-bearing effluents despite their energy demands and secondary waste generation.
Scaling up will also require answers about long-term stability, regulatory acceptance, and integration with existing mine infrastructure. Operators and regulators will want clear evidence that live cultures can be contained, that uranium-bearing precipitates remain stable under changing geochemical conditions, and that spent biomass can be handled safely, potentially as a concentrated radioactive solid for disposal. Pilot plants will need to demonstrate that the self-regenerating FeS coating maintains its function over many cycles under real-world fluctuations in pH, competing ions, and organic matter. If those hurdles can be cleared, solar-powered bacterial biohybrids could offer mining regions and legacy uranium sites a way to cut treatment costs and chemical use while sharply reducing the radiological burden released to surrounding water bodies.
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*This article was researched with the help of AI, with human editors creating the final content.
