Studies on the structure of lipopolysaccharides of Salmonella minnesota and Salmonella typhimurium R strains.

1. The composition of the lipopolysaccharides and the corresponding lipid-free polysaccharides from four R-mutants of Salmonella has been studied. All the lipopolysaccharides, from RI and RII serotypes contained d-glucose, d-galactose, heptose, N-acetylglucosamine and 3-deoxy-2-oxo-octonate. The polysaccharide obtained from the RII lipopolysaccharides also contained all these sugars. The polysaccharides from RI lipopolysaccharides lacked N-acetylglucosamine. 2. From partial hydrolysates of the lipopolysaccharides, a number of oligosaccharides have been isolated and partially characterized. Oligosaccharides containing N-acetylglucosamine or glucosamine were obtained only from RII lipopolysaccharides. Several oligosaccharides composed of glucose and galactose were common to RI and RII preparations. 3. A structural unit, based on the oligosaccharides found, is proposed for the RII lipopolysaccharide. It contains the sequence: alpha-N-acetylglucosaminyl- alpha-glucosyl-alpha-galactosyl-glucosyl.... A second alpha-galactosyl residue is bound to position 6 of the last glucosyl group. The complete unit is believed to to be attached to a polyheptose phosphate backbone in the RII antigen. 4. The RI lipopolysaccharide of Salmonella minnesota contains an analogous structure lacking the terminal N-acetylglucosamine residue. 5. A basal structure common to the lipopolysaccharides of several Salmonella species is proposed.