Primary Role of the Cytoplasmic Membrane in Thermal Acclimation Evidenced in Nitrate-Starved Cells of the Blue-Green Alga, Anacystis nidulans.

The lipid phase transition of the cytoplasmic membrane and the chilling susceptibility were studied in nitrate-starved Anacystis nidulans cells. Nitrate starvation resulted in the disappearance of the thylakoid membrane system, without any effect on chilling susceptibility. The chilling susceptibility of the algal cells depended on the growth temperature. Temperatures of lipid phase transitions of the cytoplasmic membranes were detected by chilling-induced spectral changes in the carotenoid region, in vivo. These values were identical to those of cultures containing intact thylakoid systems. Our results suggest that cytoplasmic membrane plays a determinative role in the thermal acclimation of the alga cells.