The bacteria displaying a high growth rate were isolated from polluted industrial waste water. The bacteria Enterobacter sp. had variable resistant to heavy metals such as Cd, Cu, Co, Zn and Pb. Out of which the minimal inhibitory concentrations were 0.4, 1.0, 1.0, 2.0 and 3.0 mM, respectively. The potent bacterium had optimal biosorption capacity raised according to the metal, incubation temperature, pH of the solution and contact time. Under the optimal conditions, the bacterium was capable of taking up the heavy metals Cd, Cu, Co, Zn and Pb at 2.69, 1.87, 3.56, 4.3 and 5.6 mg/g dry weight respectively. Transmission electron microscopy showed accumulation of Pb within and external to bacterial cells. The mechanism of heavy metal tolerance in Enterobacter sp. was plasmid encoded, the occurring band marked at RF had values of about 2700 Kbp.
Key words: Heavy metals uptake, heavy metals resistance, bacterial biosorption, plasmid, Enterobacter sp.
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