The study of heavy metals cadmium and zinc resistance in Escherichia coli strains isolated from surface water of Tehran using serial dilution in tube

Aim and Heavy metals are such as pollutant nature, under functions such as mining and industrial waste to entering the environment. Heavy metals including mercury, cadmium, nickel, arsenic, copper, lead, cobalt, silver and chrome. Some heavy metals are needed for cell growth in small amounts and it is toxic in high concentrations. High concentrations of heavy metals are created serious problems for the life of plants, animals, fishes and finally to humans who are the main consumers of these food sources. Identifying bacteria resistant to heavy metals plays an important role in relation to environmental pollution and eventually its cleanup. Therefore, in this study, the molecular heavy metal resistance in Escherichia coli strains isolated from surface water has been studied.
In this study, 120 samples of surface water in Tehran in the spring and summer of streams, rivers and sewage were collected and using capped sterile Falcon transported to the laboratory immediately. The first samples were enriched in the BHI broth culture. Then to see colonies of microorganisms, were cultured on BHI agar linear and were incubated at 37 ° C for 24 hours. To isolate strains from other bacteria grown in culture medium, used Eosin methylene blue (EMB) specific medium. Using the disk plate and serial dilution in the tube method, the resistance of bacteria to different concentrations of salt heavy metals zinc and cadmium sulfate was studied.
Only 40 (33/33%) E. coli strains was isolated.The minimum inhibitory concentration (MIC) was reported for zinc sulfate salt was 12/5 mM and for cadmium sulfate salt was 10 mM.
By comparing heavy metal zinc and cadmium resistant in E. coli strains was found that the amount of zinc in surface water study is more than cadmium. So the zinc resistant in Escherichia coli strains is more. Generally increase in heavy metals in surface water results in increased resistance of Escherichia coli strains to heavy metals.