Somatic Antigens of <i>Shigella</i>

Abstract

The O‐specific polysaccharide obtained from the lipopolysaccharide of Shigella dysenteriae type 1 ( Shigella shiga ) by mild acid hydrolysis followed by fractionation on Sephadex G‐50 was found to be identical to that described by Morgan's group and was composed of l ‐rhamnose, d ‐galactose and N‐acetyl‐ d ‐glucosamine in a ratio 2:1:1. On the basis of methylation analysis data the polysaccharide was proved to be a linear chain of monosaccharide residues in pyranose forms substituted at position 3, except for that of galactose substituted at position 2. Selective cleavage, based on the N‐deacetylation reaction of the polymer, together with determination of linkage configurations by chromic anhydride oxidation showed that the O‐specific polysaccharide is built up of repeating tetrasaccharide units whose proposed structure is given below ‐3)‐α‐ l ‐Rhap(1–3)‐α‐ l ‐Rhap(1–2)‐α‐ d ‐Galp(1–3)‐α‐ d ‐GlcNAcp(1‐ where Rhap = rhamnopyranose, Galp = galactopyranose, and GlcNAcp = N ‐acetyl‐glucosamine. The present findings confirmed the considerations of Heidelberger on the substitution patterns of l ‐rhamnose and d ‐galactose residues from the results of serological studies.