EFFECTS OF ADAPTATION TO DIFFERENT SALT CONCENTRATIONS ON PHOTOSYNTHESIS AND PIGMENTATION OF THE CYANOBACTERIUM SYNECHOCYSTIS SP PCC-6803

After adaptation of Synechocystis sp. PCC 6803 to different salt concentrations the growth optimum was found to be around 342 mM NaCl. At this salinity photosynthesis per cell-volume and the contents of chlorophyll and phycocyanin showed the highest values. Based on pigment contents maximal photosynthesis was measured in cells adapted to the highest salt concentration of 1026 mM NaCl. Therefore, it was concluded that in less pigmented cells the absorbed light could be more efficiently used for photosynthesis than in cells with excess pigment contents. In fluorescence emission spectra, inefficient energy transfer between phycobilisomes and chlorophyll was measured in cells rich in phycocyanin growing at 342 mM NaCl. Adaptation to higher salt concentrations also led to changes in the content and composition of the carotenoids. In cells adapted to 1026 mM NaCl the highest contents of carotenoids, especially echinenone and glycosidic carotenoids, were detected.