Study on heavy metal resistant fecal Coliforms isolated from industrial, urban wastewater in Arak, Iran

In this essay, the heavy metal resistance patterns of bacterial strains isolated from industrial wastewater, domestic wastewater and various parts of the wastewater treatment system of Arak city have been studied. 28 intestinal bacterial strains were screened and identified as Klebsiella, Escherichia coli, Citrobacter and Enterobacter species biochemical methods. The minimum inhibitory concentration (MIC) against the various heavy metals including cadmium chloride, nickel sulfate, mercuric chloride, potassium chromate and potassium tellurite were determined using the agar dilution method and some antibiotics by disk method. In this study, for first time, we have found high MIC for Klebsiella sp., 22 mM (4032 ?g/ml) for cadmium, 20 mM (3884 ?g/ml) for chromium, 20 mM (6157 ?g/ml) for telluride, 10 mM (2628 ?g/ml) for nickel and 1mM (271.5 ?g/ml) for mercury. Furthermore, the bacterial strain Escherichia coli DH5? was transformed with plasmid isolated from Cd2+ resistant Klebsiella sp. The same size of the plasmid was isolated from transformed E.coli DH5? and separated on 0.8% agarose gel electrophoresis. The curing was carried out by exposing cell culture overnight to Sodium Dodechyl Sulphate, which resulted in losing their resistance to cadmium, and therefore, the ability of Klebsiella sp. resistant to cadmium is plasmid mediated.