Biochemical Studies on Lipopolysaccharides of Salmonella R Mutants

Analyses performed on the lipopolysaccharides of several Salmonella R‐mutants as well as on their acid degradation products revealed differences in their phosphate content. Two groups of lipopolysaccharides (P + and P − ) could be distinguished, differing by approximately one phosphate group per two heptose units. The additional phosphate group in P + lipopolysaccharides is linked to the heptosyl‐heptose unit, since heptose phosphate esters could be isolated by the procedure of Slein and Schnell. When degraded P + polysaccharides were subjected to methylation and methanolysis no peaks of methylated or partially methylated heptose were detected by gas chromatography. Gel filtration on Sephadex revealed that P + degraded polysaccharides contain heterogenous fractions of higher molecular weight, while the corresponding hydrolysates from P − mutants contain only oligosaccharides of lower molecular weight. Accordingly, P − “lipopolysaccharides” are termed “glycolipids”. It is concluded, that the additional phosphate groups function as diester bridges, thus causing the formation of larger molecules. P + lipopolysaccharides and P − glycolipids of corresponding chemotypes were found to be distinct serologically when tested by hemagglutination inhibition.