Lipid and protein composition of membranes of Bacillus megaterium variants in the temperature range 5 to 70 degrees C

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Abstract
Membranes were prepared from 4 temperature range variants of B. megaterium: 1 obligate thermophile, 1 facultative thermophile, 1 mesophile and 1 facultative psychrophile, covering the temperature interval between 5-70.degree. C. The following changes in membrane composition were apparent with increasing growth temperatures: the relative amount of iso fatty acids increased and that of anteiso acids decreased, the ratio of iso acids to anteiso acids being 0.34 at 5.degree. C and 3.95 at 70.degree. C, and the pair iso/anteiso acids thus seemed to parallel the pair saturated/unsaturated acids in their ability to regulate membrane fluidity; the relative amount of long-chain acids (C16-18) increased 5-fold over that of short-chain acids (C14 and C15) between 5-70.degree. C; the relative amount of phosphatidylethanolamine increased, and this phospholipid accordingly dominated in the thermophilic strains, but diphosphatidylglycerol was predominant in the 2 other strains; and the ratio of micromoles of phospholipid to milligrams of membrane protein increased 3-fold between 5-70.degree. C. A quantitative variation in membrane proteins was evident between the different strains. Briefly, membrane phospholipids with higher melting points and packing densities appeared to be synthesized at elevated growth temperatures.

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