The polar lipids of group B Streptococci: II. Composition and positional distribution of fatty acids

Abstract

1. 1. The polar lipids from group B Streptococci have been isolated. Unless overlapping fractions are worked up on each step molecular species can be lost resulting in a fatty acid composition different from the original one. 2. 2. The lipids were shown to be 1(3), 2- diacyl-3(1)-O- α- d- glucopyranosyl-sn- glycerol , 1(3), 2- diacyl-3(1)-O-[ α- d- glucopyranosyl-(1,2)-O- α- d- glucopyranosyl]-sn- glycerol, 1,2- diacyl-sn- glycero-3- phospho-1′-sn- glycerol , lysylphosphatidylglycerol and 1′,3′-bis(1,2-diacyl- sn-glycero-3-phospho-glycerol. The stereochemical configuration of the phospholipids was achieved by combinations of chemical degradations. 3. 3. The fatty acid composition of group B Streptococci lipids is qualitatively the same as in other Streptococci, but differs by a high content of stearic acid and by a low degree of unsaturation and cyclopropanization. 4. 4. The forementioned polar lipids as well as the glucosyldiphosphatidylglycerol, which is also found in this organism, showed a very similar composition and the same non-random positional distribution of fatty acids. Apart from short chain fatty acids the positioning differentiates between saturated and unsaturated fatty acids: short chain and unsaturated fatty acids are accumulated at Position 2, saturated acids are preferentially linked to Position 1. 5. 5. The uniform fatty acid make-up in all polar lipids favours the hypothesis that their diacylglycerol portions are derived from a common phosphatidic acid precursor with negligible postsynthetic rearrangements of the constituent fatty acids.