Acta Pharm. 55 (2005) 93-105

Uranium uptake by some locally isolated and some reference bacterial species

ZAHIRA TAWFIK^1,*, MOHAMED ABU-SHADY¹ and  MOHAMED HAYTHAM²

drzahira@hotmail.com

¹National Center for Radiation Research and Technology Atomic Energy Authority
²Ain Shams University, Cairo, Egypt

In the present study, uranium absorption capacity of Bacillus pantothenticus and Bacillus megaterium, previously isolated from the environmental air surrounding the ⁶⁰Co gamma source, is reported. Pseudomonas putida and Pseudomonas chlororaphis were used as reference species. Concerning uranium uptake, the local species were more efficient than the reference ones. The maximum uptake was achieved by B. megaterium and B. pantothenticus at 20 microgram U mL^-1 and by B. pantothenticus at 30 microgram U mL^-1. The transmission electron microscope examination indicated that uranium was absorbed onto the cell surface of the studied isolates. Furthermore, the increase in biomass concentration has shown an increase in the total amount of uranium removed. Dead cells exhibited uranium uptake to the same or greater extent than living cells. B. pantothenticus, P. putida, and P. chlororaphis achieved maximum uptake at pH 4.0, whereas B. megaterium it was pH 6.0. Temperature had an important role in uranium absorption of all the studied species except B. pantothenticus,. Metabolic inhibitors did not affect the uptake.

Keywords: uranium uptake, bacteria