The O9 antigen of Escherichia coli. Structure of the polysaccharide chain

The lipopolysaccharide from Escherichia coli O9:K30- was isolated in about 2% yield with aqueous 45% phenol at 65 degrees C, followed by ultracentrifugation. The polysaccharide moiety was obtained by graded hydrolysis and gel permeation chromatography. It consisted of a mannan which carried on its reducing end the core oligosaccharide of the R1 type. The mannan contained 1 leads to 2 and 1 leads to 3 linkages in a ratio of 3:2, as determined by methylation analysis and mass spectrometry. On periodate oxidation, 58% of the mannose residues were destroyed. Degradation of oligosaccharide mixtures with alpha-mannosidase from jack bean meal, as well as a specific rotation of [alpha]25D = +89 degrees indicated that all mannosyl linkages have the alpha-configuration. Smith degradation resulted in the liberation of mannosyl (1 leads to 3)-mannose (bound to glyceraldehyde), as established by methylation analysis. From these results we conclude that the O9 polysaccharide of E. coli has a pentasaccharide repeating unit of alpha-mannosyl(1 leads to 3)-alpha-mannosyl-(1 leads to 2)-alpha-mannosyl-(1 leads to 2)-alpha-mannosyl-(1 leads to 2)-mannose, which are joined in the polysaccharide through alpha-(1 leads to 3)-mannosyl linkages.