Effect of pH pretreatment on growth and photosynthetic properties of cyanobacterium Fischerella sp. FS 18

For the first time, the effect of pretreatment of time (24 and 96 hours) and pH (7 and 9) at extremely limited carbon dioxide concentration on the exponential growth phase, photosynthetic pigments per cell, absorption shift of chlorophyll, structure and function of phycobilisome, light harvesting to reaction center pigment and photosystem one to photosystem two ratios were studied on stigonematalean cyanobacterium Fischerella sp.FS 18. Results showed that pretreatment treatments cause keeping the exponential growth phase at both 24 and 96 hours and pHs 7 and 9. In the opposite of absorption peak of chlorophyll, cellular pigments show no stable pattern regarding pretreatments. Phycobilisomes was the main point of treatment affects. The pattern of the rode part of phycobilisomes was the same at pretreatment reactions. The shift of phycocyanin was about one and phycoerythrin about nearly three. The highest rate of photosystem one to photosystem two ratio observed at 24 hours’ neutral condition. This changed by the time and caused efficiency decreasing of energy transport in photosynthesis system. Phycobilisome operation change may be a compensational mechanism to reduce the degree of such a decrease.