Structural features of a lipopolysaccharide isolated from Escherichiacoli 086:Kneg.

Lipopolysaccharide (LPS) prepared from Escherichiacoli 086:Kneg., in 5.5% yield contained D-galactose, D-glucose, L-fucose, L-glycero-D-manno-heptose, D-glucosamine, D-galactosamine, 2-keto-3-deoxy-octulosonic acid (KDO) and lipid A. The molecule appeared to be homogeneous as tested by free boundary electrophoresis, ultracentrifugation, and immunodiffusion against ′O′ specific E. coli antiserum. Methylation studies of the LPS and also of the degraded polysaccharides obtained by partial acid hydrolysis showed that the molecule was highly branched. Sixty percent of the D-galactose units were non-reducing terminal groups, the remainder were linked (1 → 3) and (1 → 2) and 3-O-β-D-galactopyranosyl-D-galactose was identified as a product of mild acid hydrolysis of the parent LPS. Fucose occurred in the polysaccharide as (1 → 4) linked units. Methylation results showed that the D-glucose units were linked (1 → 3) and (1 → 4). Partial acid hydrolysis yielded cellobiose, cellotriose, and laminaribiose, showing that the glucose units formed a glucan chain within the polysaccharide and that the glucosidic linkages were in the β-D-configuration. Approximately one half of the L-glycero-D-manno-heptose units occurred as non-reducing end groups, the other half were linked at C-3 and either one of C-6 or C-7. One half of the D-galactosamine units was linked (1 → 3) with the remainder occurring as double branch points. D-Glucosamine residues occurred exclusively in the lipid A moiety in a (1 → 4) linked core structure.