Investigation of Growth Rate, Resistance, and Zinc Elimination Ability of Resistant Bacteria Isolated from Water and Sediment of Karun River

Although zinc is an essential metal ion، however، its high concentration is toxic and has inhibitory effect on important functions of the cells. Purpose of present study is investigation of growth rate، resistance، and zinc elimination ability of isolated bacteria from Karun River. In this research water and sediment samples were taken from 4 stations in 3 seasons. Isolation of resistant bacteria was performed by enrichment and direct culturing on solid medium. Isolated bacteria were identified by using biochemical tests and their resistance was evaluated in LB broth medium containing 200 to 1400 mg/l of zinc chloride. Growth of resistant bacteria and their ability to remove zinc were investigated at zinc chloride concentration of 260 mg/l. Bacteria such as Pseudomonas، E. coli، Salmonella، and Citrobacter were identified as zinc resistant bacteria. Some of the bacteria were able to tolerate 1000 mg/l of zinc chloride concentration. Zinc removal ability of bacteria isolated in each season varied from 39 to 68 %. Pseudomonas isolated in summer showed the highest growth in presence of zinc. Isolated bacteria from zinc contaminated sites have the potential for zinc elimination. Growth curves of resistant bacteria followed standard growth curves in presence of 260 mg/l of zinc chloride. Pseudomonas isolated in summer showed the highest zinc removal rate with an efficiency of 68%.