Effect of growth temperature on the lipids of Pseudomonas fluorescens

Pseudomonas fluorescens was grown in co ntinuous culture with glucose or NH4+ as the growth-limiting substrate. The total amount of lipid and the relative proportions of neutral lipid and phospholipid did not vary with the rate or temperature of growth. The amounts of the phospholipids, which were phosphatidyl glycerol, cardiolipin and phosphatidyl ethanolamine, altered with the type of growth limitation and with the temperature and rate of growth. A precise composition of phospholipid classes is not a requirement for growth at low temperature. Fatty acid composition also varied with changes of these growth conditions at temperatures above 10 degrees C, but at lower growth temperatures the degree of saturation of the lipids was strictly controlled, and was unaffected by changes in the growth rate or the nature of the growth-limiting substrate. The degree of saturation of the lipids was not critical at the higher growth temperatures, and the variation in the degree of saturation observed at these temperatures was due in part to a decreased ability of the organism to control the fatty acid composition of its lipids at temperatures above 10 degrees C.