[Intracellular oxygen and the radiosensitization of cells of the blue-green alaga, Anacystis nidulans].

The photosynthetic system of the blue-green alga Anacystis nidulans was inactivated by 30% at a dose of 100 krad of gamma irradiation in N2. If the cells were irradiated in N2+2% CO2 in the light, their radiation sensitivity was increased with an oxygen enhancement ratio of 2.0. Neither light nor CO2 taken separately affected radiosensitization of the cells which increased almost to the same extent as under aerobic conditions in the presence of both light and CO2. The intracellular oxygen of the photosynthetic origin caused apparently the same radiosensitization as oxygen derived from the extracellular sources.