Influence of the sanosil-induced oxidative stress on the photosynthetic apparatus of different strains of green algae and cyanobacteria

Photosynthetic oxygen evolution (measured by polarographic oxygen rate electrode) and pulse amplitude modulated chlorophyll fluorescence were used to assess the effect of sanosil-induced oxidative stress on photosystem II (PSII) in the green alga Chlorella vulgaris and the cyanobacterium Synechocystis salina isolated from Antarctic and mesophilic environments. This study revealed a relatively stronger influence of sanosil (especially its main component, hydrogen peroxide) on the donor site (oxygen evolving complex) compared to the acceptor side of the PSII in both green algae and cyanobacteria. The inhibition of the oxygen evolution results mainly from a decrease in the fast operating PSII centers. In addition, the obtained data showed that the effects of the oxidative stress on the cyanobacterium and the green alga strongly depend on the antenna size of PSII.