Phospholipid composition and heat sensitivity in a thermophilic bacterium.

A Gram-negative thermophilic bacterium designated strain LEH-1, survived under non-growth conditions, temperatures 5 degrees C above its maximum for growth when acetate or n-heptadecane served as carbon source, whereas cells grown with glucose or glycerol were markedly more sensitive to elevated temperatures. The total extractable lipids from strain LEH-1 and the concentrations of phosphatidylethanolamine and phosphatidic acid in the cytoplasmic membranes was altered by the growth substrate. Growth with acetate of n-heptadecane as carbon source yielded cells containing more phosphatidic acid than phosphatidylethanolamine. Conversely, more phosphatidylethanolamine was present in cells following growth with glucose or glycerol as carbon source. The relative amount of specific fatty acids and distribution in major phospholipid moieties was also affected by the growth substrate. These differences in composition may reflect an alteration in the physical properties of the cellular membrane and account for the divergence in heat sensitivity.