The following structure of the O-specific polysaccharide chain (O-antigen) of the Proteus vulgaris O32 lipopolysaccharide (LPS) was established by 1 H-NMR and 13 C-NMR spectroscopy, including twodimensional NOESY and H-detected 1 H, 13 C heteronuclear multiple-quantum coherence (HMQC) experiments:In addition, an O-acetyl group was detected, which, most probably, is located at position 3 of a part of Rhap I residues. Serological studies, using rabbit polyclonal anti-(P. vulgaris O32) serum, homologous and heterologous Proteus O-antigens and related artificial antigens, revealed the importance of an A-D-GalA-associated epitope in manifesting the immunospecificity of P. vulgaris O32 and substantiated serological relationships between the O-antigen studied and those of some other Proteus strains.Keywords : Proteus vulgaris ; lipopolysaccharide; O-antigen; bacterial polysaccharide structure; serological specificity.Bacteria of the genus Proteus cause mainly wound and urinary tract infections, the latter sometimes leading to acute or chronic pyelonephritis and formation of bladder and kidney stones. Outer membrane lipopolysaccharide (LPS, endotoxin) is considered as a virulence factor of Proteus. Based on the Ospecific polysaccharide chains of LPS (O-antigens), two species, Proteus mirabilis and Proteus vulgaris, were classified into 60 O-serogroups [1, 2], and recently two more O-serogroups, O61 and O62, have been proposed for strains of the third species, Proteus penneri [3,4]. Chemical and immunochemical studies of Proteus LPS are important for understanding the molecular basis of the immunospecificity of Proteus strains and for their classification based on structural and serological data.A peculiar feature of the Proteus LPS is that in most Oserogroups the O-antigens are acidic due to the presence of phosphate groups, hexuronic acids, their amides with amino acids, sugar acetals with pyruvic acid or ethers with lactic acid ([3Ϫ9] and references cited therein). The role of acidic polysaccharides in the pathogenicity of Proteus and, particularly, in urinary tract infections was discussed [10]. The acidic character of Proteus polysaccharides enables bacteria to bind metal cations, Mg 2ϩ and Ca 2ϩ , via electrostatic interaction. This may enhance the formation of struvite and carbonate apatite stones in urinary tract under alkaline conditions in the presence of ammonia, one of the products of urea decomposition caused by Proteus bacteria [11]. Recently, the importance of an acidic polysaccharide rich in galacturonic acid and galactosamine was demonstrated for migration of P. mirabilis swarm cells by reduction of surface friction [12].A few structures of P. vulgaris O-antigens have been elucidated, some of them having been found neutral [7,13] and the others acidic [7Ϫ9]. Now, we report the structure of a new acidic O-specific polysaccharide of P. vulgaris O32 containing D-galacturonic acid.
MATERIALS AND METHODSBacterial strains, growth, isolation and degradation of lipopolysaccharide. P. vulgaris O32 (strain PrK 57/...