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 of uranium was achieved by B. megaterium and P. chlororaphis at 20 microg U mL(-1) and by B. pantothenticus at 30 microg 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 for B. megaterium it was at 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.