Selenium metabolism in the Marine phytoplankters Tetraselmis tetrathele and Dunaliella minuta

Radioactive selenite-75 has been used to investigate the metabolic transformation of inorganic selenium by the marine phytoplankters Tetraselmis tetrathele and Dunaliella minuta. The majority of radioselenium taken up from culture media during growth becomes associated with cellular protein. A small quantity of this protein-bound selenium can be volatilised by treatment with strong acid, suggesting the presence of hydrogen selenide. However, the principal fraction of selenium appears to be integrated into the primary protein structure. Enzymic hydrolysis of phytoplankton protein and subsequent chromatography of hydrolysates revealed the presence of seleno-analogues of the sulphur amino acids. Selenium amino acids were also detected in non-protein extracts.