Identification of a novel core type in Salmonella lipopolysaccharide. Complete structural analysis of the core region of the lipopolysaccharide from Salmonella enterica sv. Arizonae O62

For the first time, the complete structure of a lipopolysaccharide (LPS) core region from Salmonella enterica has been identified that is different from the Ra core type generally thought to be present in all Salmonella LPS. The LPSs from two rough mutants and the smooth form of S. enterica sv. Arizonae IIIa O62, which all failed to react with an Ra core type-specific monoclonal antibody and were resistant to phage FO1, were analyzed after chemical modification using monosaccharide analysis, mass spectrometry, and NMR spectroscopy. In the novel core type, the terminal D-GlcNAc residue present in the Ra core type, is replaced by a D-Glc residue. The O-specific polysaccharide is alpha1-->4-linked to the second distal Glc residue of the core. Furthermore, phosphoryl substituents attached to O-4 of L-glycero-D-manno-heptose (Hep) I and II were identified as 2-aminoethyl diphosphate (on Hep I) and phosphate (Hep II). [structure: see text] Abbreviations in Structure I are as follows: Hepp, L-glycero-D-manno-heptopyranose; Kdo, 3-deoxy-D-manno-oct-2-ulopyranosonic acid; PPEA, 2-aminoethyl diphosphate; R, O-specific polysaccharide. The presence of this novel core type in LPS of S. enterica should be taken into account in the development of a general antibody-based diagnostic system for Salmonella.