Acclimation of a mesophilic cyanobacterium, Synechocystis sp. PCC 6803 to the growth temperature

Abstract

Photosynthetic organisms usually experience large changes of environmental factors, such as temperature, light intensity or light quality. Temperature is one of the most important factors which control the enzymatic reaction including photosynthesis. They may regulate the total reaction system to operate the photosynthesis maximally for their survival. In higher plants, acclimation to the surrounding temperature has been reported. Here, we analyzed the effect of temperature, especially that of high temperature, on the growth using a mesophilic cyanobacterium, Synechocystis sp. PCC 6803. The following results were obtained. (1) Photosynthesis seemed to be regulated so as to keep its rate in a certain range irrespective of the growth temperatures. (2) The oxygen-evolving activity and the intactness of plasma membranes showed larger tolerance to high temperatures when S. PCC 6803 cells were grown at higher temperatures. (3) The reaction center activity of photosystem II (PS II) showed similar sensitivity to the heat stress when the activity was measured at the growth temperatures irrespective of the growth temperature. However,small but distinct temperature acclimation of the PSII reaction center activity was shown for the cells grown at different temperatures when the activity was measured at inhibitory high temperatures. (4) A close relationship was observed between the viability of cells and the structural changes of plasma membranes (not the inactivation of photosynthesis). We will discuss how the S. PCC 6803 cells acclimate to the environmental temperature.