STRUCTURE OF THE O-SPECIFIC SIDE-CHAIN OF THE LIPOPOLYSACCHARIDE FROM ESCHERICHIA-COLI O126

The polysaccharide isolated from Escherichia coli O126 lipopolysaccharide 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 compositional analysis, partial degradation, methylation analysis, and nuclear magnetic resonance spectroscopy. These studies revealed that the O-antigen is branched and built up of tetrasaccharide repeating units having the following structure: [GRAPHICS] C-13 NMR spectra of C-13-labeled SSG (C-13-SSG) revealed that a strong signal of the C-13-nucleus was 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 glucose 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 all 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.