Light-induced changes of radioactivities in the 14C-labeled lipids and fatty acids of dark grown Euglena gracilis.

Euglena gracilis was grown in the dark for 12 days in a medium containing sodium acetate1-14C. The major amount of 14C was incorporated into the neutral lipids. In these compounds myristic acid was the main fatty acid labeled. Subsequent growth in light (70 hours) in an iden­ tical medium (containing unlabeled acetate) led to a strong decrease of radiocarbon in the neutral lipids. The radioactivities in phosphatidyl choline and phosphatidyl ethanolamine increased during the first 28 hours of illumination and thereafter decreased. The radioactivities in phosphatidyl glycerol, sulfolipid, monogalactosyl diglyceride and digalactosyl diglyceride increased continously. After 70 hours of illumination, most of the radiocarbon was detected in the saturated and un­ saturated Cie and C18 fatty acids of these four lipids. The possibility of light-induced transfers of fatty acids from neutral lipids via phospholipids to