The lipoteichoic acid (LTA) is a specific polymer on Gram-positive bacterial cell surfaces, and is not found in Gram-negative bacterial cells. LTA is an amphipathic anionic polymer typically comprised of poly-glycerophosphate (GroP) linked to glycolipid of cell membrane. In general, hydroxyl groups of GroP residues in polymer region are often substituted by D-alanine and/or carbohydrates. Glycolipid anchor typically comprises diglycosylglycerolipid containing two acyl groups. On the other hand, structural variation on species-or strain-level has been observed in degree of polymerization, substitution ratio of the GroP repeating unit, and numbers of carbohydrate and acyl groups in glycolipid moiety. However, structural information has not sufficiently accumulated to discuss unity and diversity of LTA structures.
We determined chemical structure of LTA derived from seven strains of Lactobacillus gasseri, an intestinal lactic acid bacterium. All strains shared common structure. Polymer chain comprised poly-GroP with partial substitution with D-alanine. Glycolipid anchor contained novel tetrasaccharide structure and two or three acyl groups. The three acyl group-containing glycolipid anchor is characteristic LTA structure in lactic acid bacteria, including Lactobacillus genus, Lactococcus genus and Leuconostoc genus. The tetrasaccharide structure has not been reported in other Gram-positive bacterial LTA. In conclusion, the tetrasaccharide-containing glycolipid anchor is unique and species-specific LTA structure in L. gasseri.
