Glucosylation of Lipopolysaccharide in Salmonella: Biosynthesis of O Antigen Factor 122

Salmonella mutants defective in the biosynthesis of the central R core portion of cell wall lipopolysaccharide accumulate the peripheral side portion of lipopolysaccharide in a form presumably linked to the lipid carrier. When such an O side chain polysaccharide was isolated from a core-defective mutant derived from a Salmonella typhimurium strain originally producing O antigen 122, the polysaccharide was found to possess the full determinant group for 122 antigen, i.e. short side chains each consisting of a single α-d-glucopyranosyl residue linked to C-4 of d-galactose. However, the galactose residue at the reducing end of the O side chain did not appear to have been glucosylated. These results suggest that the transfer of the foregoing glucose residues normally takes place at the level of the carrier-linked oligomers of O side chain-repeating units, rather than at the level of the repeating unit monomers or at that of the lipopolysaccharide.