Structure of Cell Wall Lipopolysaccharide from Salmonella typhimurium IV. Anomeric Configuration of l-Rhamnose Residues and Its Taxonomic Implications

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A major portion of cell wall lipopolysaccharide from group A, group B, or group D1Salmonella corresponds to a linear polysaccharide chain, which consists of α-d-galactosyl-(1 → 2)-α-d-mannosyl-(1 → 4)-l-rhamnosyl-(1 → 3)-repeating units, and has short branches of single 3,6-dideoxyhexose residues. The groups differ in the configuration of the 3,6-dideoxyhexose present. Furthermore, it has been claimed that the anomeric configuration of the rhamnosyl residues is β-l in group B, in contrast to the α-l configuration found in groups A and D1. In this study, oligosaccharides containing more than one repeating unit were isolated from a lipopolysaccharide of a group B Salmonella, and the anomeric configuration of the rhamnosyl residues was determined by the comparison of optical rotatory powers of these oligosaccharides with that of the repeating unit trisaccharide. The results established the configuration of rhamnose as α-l, in contrast to the β-l configuration suggested in the literature. Since rhamnosyl linkages in lipopolysaccharide of a group D1Salmonella are hydrolyzed in acid at exactly the same rate as are those in group B Salmonella, the configuration of rhamnose residues in groups D1 lipopolysaccharide is also likely to be α-l. These results indicate that lipopolysaccharides of Salmonella groups A, B, and D1 share an identical main chain polysaccharide and differ essentially only in the configuration of 3,6-dideoxyhexose branches; they thus suggest close evolutionary relationship between these three serogroups of Salmonella.

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