Phase separations in membranes of Anacystis nidulans grown at different temperatures

Freeze fracture electron microscopy studies were performed on samples of Anacystis nidulans quenched from different temperatures. Membrane lipid phase separations were observed to take place over the ranges 15--30 degrees C, 5--25 degrees C and -5--15 degrees C for cultures grown at 38, 28 and 18 degrees C, respectively. Differential scanning calorimetry heating curves showed endotherms which coincided with these temperature ranges. Variations of phase separation temperatures with growth temperature, and hysteresis effects in the calorimetric measurements, were related to changes in the fatty acid composition of membrane lipids.