PHOTODYNAMIC-ACTION OF HYPERICIN ON CYANOBACTERIA, SYNECHOCYSTIS AND SYNECHOCCUS (ANACYSTIS-NIDULANS)

The photodynamic action of hypericin on photosynthesis and respiration were monitored in Synechocystis sp PCC 6803 and Synechoccus ATCC 6311 (Anacystis nidulans). An oxygen electrode was used to measure net oxy gen evolution or consumption. The amount of hypericin required to inhi bit photosynthesis was quantitively determined. Photosynthesis was com pletely inhibited in Synechocystis when the molar ratio of chlorophyll /hypericin was about 70:1. Higher concentrations of hypericin did not stop the uptake of oxygen, but rather stimulated the process in the li ght. Hypericin was readily washed out of the cells forming no permanen t associations in the bacterial cell. Hypericin inhibited electron tra nsfer and consequently oxygen production by PSII particles. For half m aximum inhibition of oxygen evolution, with PSII membrane particles, t he molar ratio of chlorophyll/hypericin was about 10:1.