Temperature-dependent lipid content and fatty acid composition of three thermophilic bacteria.

The lipid content and fatty acid composition of a strain of Bacillus caldolyticus and of two facultative thermophiles (B. flavothermus and strain NZ-2) were analysed after growth at different temperatures. In all three strains the amount of membrane, as a fraction of total cellular dry mass, was found to increase with temperature, however, in varying degrees. Changes of lipid content and protein/lipid ratio in B. caldolyticus between 60 degrees C and 100 degrees C and in strain NZ-2 between 45 degrees C and 70 degrees C were minor; in B. flavothermus the alterations in the 50 degrees C-70 degrees C range were more pronounced. The same was found for changes observed in the phospholipid/total lipid and phospholipid/membrane ratios, and also in the amounts of individual phospholipids. The alterations of the fatty acid composition were most significant in B. caldolyticus, especially between 80 degrees C and 95 degrees C. In contrast, the main changes in B. flavothermus and NZ-2 were found to occur between 30 degrees C and 50 degrees C, and between 45 degrees C and 60 degrees C, respectively. Based on these data, strain NZ-2 could be characterized as the least and B. flavothermus as the most versatile of the three organisms.