Abstract
Selenate, selenite, selenomethionine, and selenopurine are toxic to Anacystis nidulans and Anabaena variabilis. These compounds are less toxic in culture medium containing sulphate than in sulphur-free medium, thus suggesting a protective role of sulphur against selenium toxicity Selenite is more toxic in agar plate cultures and less toxic in liquid cultures than selenate. Cells grown in the highest growth-permitting concentration of selenite in liquid medium form a variable number of red granules No such granulation occurs in cells treated with other seleno-compounds, indicating thereby that the mode of selenite action in blue-green algae differs from that of other selenium compounds