Effect of selenium on the growth of the cyanobacterium Anacystis nidulans

Direct count and turbidity were used to determine the effect of various concentrations of selenium dioxide on the growth of the cyanobacterium, Anacystis nidulans, and light microscopy and scanning electron microscopy were used to study morphology. Concentrations of 0, 10, 25, 50, and 100 mg/l were used. Results showed that growth was inhibited completely at SeO sub(2) concentrations of 50 mg/l and higher. A concentration of 25 mg/l proved to be toxic, but when EDTA was present, this concentration was not toxic, indicating that EDTA was an effective chelating agent for Se. At SeO sub(2) concentrations of 50 mg/l and higher, the number of cells was reduced sharply, and cell morphology was irregular, with many degraded cells and cellular debris. Results indicated that 50 and 100 mg/l SeO sub(2) were cyanostatic and cyanocidal with EDTA, respectively, while 25 and 50 mg/l were cyanostatic and cyanocidal without EDTA, respectively.