ISOMALTO-OLIGOSACCHARIDE-CONTAINING LIPOTEICHOIC ACID OF STREPTOCOCCUS-SANGUIS - BASIC STRUCTURE

The lipoteichoic acid of Streptococcus sanguis DSM 20567 and of DSM 20068 was isolated by phenol/water extraction and hydrophobic-interaction chromatography. The preparations from both strains have an identical structure: a 1,3-linked poly(glycerophosphate) chain phosphodiester-linked to Glc-(alpha1 - 2)Glc(alpha1 - 3)acyl2Gro as the lipid anchor. The chain is substituted with D-alanine ester and glycosyl residues which comprise mono-, di-, tri- and tetra-alpha-D-glucopyranosyl residues with (1 - 6) interglycosidic linkages. The glycosylglycerols were released with 48 % (by mass) hydrofluoric acid, separated and characterized by a combination of chemical procedures and modem techniques of H-1-NMR and C-13-NMR spectroscopy. The alpha-isomalto-oligosaccharides add a novel motif to lipoteichoic-acid chain substituents. H-1-NMR and C-13-NMR spectroscopy also provided a detailed picture of the basic glycosylated poly(1,3-glycerophosphate) diglucosylglycerol, It proved a single unbranched chain structure, provided evidence for the chain length, the extent of glycosylation, the structure of the lipid anchor and the site of attachment of the poly(glycerophosphate) chain on the lipid anchor. Owing to its unique glycosyl substituents the lipoteichoic acid may serve as a taxonomic marker for the redefined species S. sanguis (formerly S. sanguis type I).