Evaluation of Toxicity of Heavy Metals for Escherichia coli   Growth

Iron is essential to virtually all organisms but it can be toxic in excess. High concentration of iron and other trace elements could restricted bacterial growth and modify their metabolic pattern as well. However, this study aimed to find out the influence of iron, chromium, cadmium and synergism or antagonism between these elements on growth of a gram negative bacterium. In the series of experiments, Escherichia coli has been cultured in a nutrient broth which supplemented with Fe+2, Fe+3, Cr+3, Cd+2 alone or in combination with together, at 37°C for 5 h. Bacterial growth was measured every half an hour using spectrophotometer. Findings obtained from this study indicated that bacterial growth reduced at presence of 1 mM/L concentration of Fe+3 and 0.5 mM/L Fe+2 in comparison with control. Growth of the bacteria was completely inhibited by 1 mM/L concentration of iron (II). Chromium has also inhibitory effects on growth of the bacteria and cadmium is very toxic. Cr+3 and Cd+ have antagonism effect with iron on the growth of bacteria. This work suggested that trace elements could interact in their metabolism in bacteria. It has also concluded that toxic effects of trace element could be another view against pathogenic bacteria particularly in complex with antibacterial activity of various antibiotics