Optimum Biosorption and Resistance of Uranium by Metal-Resistant Bacteria Isolated from Rock Ore

Abstract

Natural environments contain a variety of microorganisms, of which, a limited number are able to develop bioremediation process. The main goal of the present paper was to perform microbiological investigations to culturable bacteria isolated from uranium ore samples from Aborshid Egypt, and characterize their response to 15 antibiotics and 10 heavy metals beside uranium. Among the potential environmental isolates, there was no detection of any acquired antibiotic resistance , which supports the idea that their resistance mechanisms are mainly intrinsic. On the contrary, the potentially pathogenic isolates presented a broad diversity of acquired antibiotic resistance toward different antibiotic classes. Furthermore, results revealed a varying response of the ore bacteria to the tested heavy metals. All isolates showed multiple metal resistances toward 10 heavy metals, with MIC ranging from 50 to 1000 ppm. We found that optimum temperature for growth of bacteria in general ranges from 30 to 50 °C and bio-sorption of metal increased with increasing pH from 1.0 to 5.0, then decreased upon further increase to 7.0. The decrease in the sorption efficiency at pH higher than 5.0 may be due to the precipitation as hydroxide. We found possible correlation between antibiotic resistance and heavy-metal resistance patterns of Escherichia coli strains isolated from uranium ore; the most potent of the strains in both groups were resistant to Pb, Ni, Cu and Zn. It was concluded that highly metal-resistant bacteria could be used with potential application for treatment of wastewaters.