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Uranium uptake by some locally isolated and some reference bacterial species
Zahira Tawfik1, Mohamed Abu-Shady, Mohamed Haytham
1National Center for Radiation Research and Technology, Atomic Energy Authority Ain Shams University, Cairo, Egypt. drzahira@hotmail.com
Acta Pharmaceutica (Zagreb, Croatia)
|May 24, 2005
Summary
Bacillus species isolated near a gamma source show high uranium absorption efficiency. These bacteria, particularly Bacillus megaterium and Bacillus pantothenticus, effectively remove uranium from solutions, with uptake occurring on the cell surface.
Area of Science:
- Environmental microbiology
- Bioremediation
- Radioactive waste management
Background:
- Microbial bioremediation offers a sustainable approach for removing heavy metals and radionuclides from contaminated environments.
- Certain bacterial species possess inherent capacities for metal ion adsorption and biosorption.
- Understanding the uranium absorption capabilities of indigenous microorganisms is crucial for developing effective remediation strategies.
Purpose of the Study:
- To evaluate and compare the uranium absorption capacity of Bacillus pantothenticus and Bacillus megaterium, isolated from a radioactive environment.
- To assess the influence of environmental factors such as pH, biomass concentration, and temperature on uranium uptake.
- To investigate the role of cell viability in the uranium biosorption process.
Main Methods:
- Isolation and identification of bacterial species (Bacillus pantothenticus, Bacillus megaterium) from air near a 60Co gamma source.
- Uranium uptake experiments using isolated strains and reference species (Pseudomonas putida, Pseudomonas chlororaphis).
- Transmission electron microscopy (TEM) for visualizing uranium localization on cell surfaces.
- Optimization studies for pH, biomass concentration, and temperature effects on uranium absorption.
Main Results:
- Local bacterial isolates, Bacillus pantothenticus and Bacillus megaterium, demonstrated higher uranium absorption efficiency compared to reference species.
- Maximum uranium uptake was observed at specific concentrations (e.g., 30 microg U mL(-1) for B. pantothenticus).
- Uranium was primarily adsorbed onto the bacterial cell surface, and increased biomass led to greater total uranium removal. Dead cells showed comparable or higher uptake than live cells.
Conclusions:
- Bacillus pantothenticus and Bacillus megaterium are highly efficient in uranium biosorption, making them promising candidates for bioremediation.
- Uranium adsorption is largely a surface phenomenon, influenced by pH and temperature, and is not dependent on active cellular metabolism.
- The use of dead biomass can be an effective strategy for uranium removal, simplifying the bioremediation process.