Structure of a new ribitol teichoic acid-like O-polysaccharide of a serologically separate Proteus vulgaris strain, TG 276-1, classified into a new Proteus serogroup O53

where the non-glycosylated ribitol residue is randomly mono-O-acetylated. An unusual ribitol teichoic acid-like O-polysaccharide was isolated by mild acid degradation of the lipopolysaccharide from a previously non-classified Proteus vulgaris strain TG 276-1. Structural studies using chemical analyses and 2D 1H and 13C NMR spectroscopy showed that the polysaccharide is a zwitterionic polymer with a repeating unit containing 2-acetamido-4-amino-2,4,6-trideoxy- d-galactose ( d-FucNAc4N) and two d-ribitol phosphate ( d-Rib-ol-5- P) residues and having the following structure: [Display omitted] where the non-glycosylated ribitol residue is randomly mono-O-acetylated. Based on the unique O-polysaccharide structure and the finding that the strain studied is serologically separate among Proteus bacteria, we propose to classify P. vulgaris strain TG 276-1 into a new Proteus serogroup, O53.