STRUCTURE OF THE O-SPECIFIC SIDE-CHAIN OF THE LIPOPOLYSACCHARIDE FROMESCHERICHIA-COLI O126

The polysaccharide isolated from Escherichia coli O126 lipopolysacchar ide contains D-galactose, D-mannose, L-fucose, and 2-acetamido-2-deoxy -D-glucose in the molar ratios 1:1:1:1. The structure of the O-antigen of the lipopolysaccharide from E. coli O126 was established by compos itional analysis, partial degradation, methylation analysis, and nucle ar magnetic resonance spectroscopy. These studies revealed that the O- antigen is branched and built up of tetrasaccharide repeating units ha ving the following structure: [GRAPHICS] C-13 NMR spectra of C-13-labe led SSG (C-13-SSG) revealed that a strong signal of the C-13-nucleus w as observed at the C-1 or C-2 position when D-[1-C-13]glucose or D-[2- C-13]glucose was used, respectively, suggesting that most of the gluco se residues in SSG were directly taken up from the medium. In addition , part of the C-13-nucleus was incorporated into the SSG molecule at a ll carbon atoms after metabolic degradation and reconstruction of the glucose molecule. Analyses of the culture filtrate and the mycelium of the fungus suggested that part of the glucose was also metabolized to trehalose and mannitol.