Cell-Wall Lipopolysaccharide of the 'Shigella-Like' Escherichia coli 0124. Structure of the Polysaccharide Chain

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Abstract
From Escherichia coli 0124 two lipopolysaccharide preparations were obtained with phenol/water extraction and cetavlon precipitation. Polyacrylamide gel electrophoresis in the presence of sodium dodecylsulfate, and chemical analysis showed that the two preparations differed only in the extent of the O-specific polysaccharide moiety. In passive haemagglutination and gel precipitation the two lipopolysaccharide preparations from E. coli 0124 and the corresponding preparations from Shigella dysenteriae type 3 reacted alike. The O-specific polysaccharide moiety was characterized with proton magnetic resonance spectroscopy, optical rotation and paper electrophoresis. The constituents were determined by gas chromatography and ion-exchange chromatography. The polysaccharide contained glucose (Glc), galactose (Gal), galactosamine (GalN) and 4-O-(1′-carboxyethyl)-d-glucopyranose (glucolactilic acid, GlcLA) in the molar ratios. of 1:2:1:1. Glucolactilic acid, which has a structure similar to muramic acid, was first found in Sh. dysenteriae. The polysaccharide from E. coli 0124 and oligosaccharides obtained from it by partial acid hydrolysis were subjected to methylation analysis using the method of combined gas chromatography-mass spectrometry. The results indicated that the pentasaccharidc repeating unit of the polysaccharide is In the polysaccharide the repeating units are joined through galactofuranosidic linkages. This structure is identical with that of the somatic polysaccharide of Sh. dysenterae type 3.