Biochemical Studies on Lipopolysaccharides of <i>Salmonella</i> R Mutants

Abstract

The endotoxically active cell wall glycolipid of a highly deficient heptose‐less R mutant of Salmonella minnesota , consisting of 2‐keto‐3‐deoxyoctonic acid (KDO) and lipid A, was subjected to hydrazinolysis. Besides fatty acid hydrazides, a water‐soluble main fraction was obtained, containing KDO, glucosamine, and ester phosphate and free phosphorylethanolamine. The application of two procedures of partial hydrolysis, followed by paper electrophoretic separation, led to seven oligosaccharides. Their structures were evaluated with the aid of the following analytical methods: further acid degradation, borohydride reduction, ninhydrin degradation, the Morgan‐Elson reaction, treatment with phosphomonoesterase and N ‐acetylglucosaminidases. The results show that the backbone of lipid A contains phosphorylated glucosaminyl→glucosamine disaccacharide units, probably linked β‐1,6, to which a trisaccharide composed of three KDO residues is linked ketosidically to form a pentasaccharide which appears to be a common structure in many Enterobacteriaceae .