Effect of copper on the growth of Anacystis nidulans

The effect of different concentrations of copper, as either copper sulphate or cupric chloride, on the growth of the freshwater cyanobacterium Anacystis nidulans, in the presence and absence of the chelating agent EDTA, was investigated in the laboratory. Inhibition of growth was due to the cupric ion alone; the concentrations of the accompanying anion had little or no effect. In the absence of EDTA, growth was inhibited by copper concentrations below 2 ppm. In the presence of 3 M EDTA, growth was inhibited somewhere between 2 and 20 ppm copper. Some environmental implications of the findings are indicated.