Somatic antigens of Pseudomonas aeruginosa. The structure of the O-specific polysaccharide chains of lipopolysaccharides of P. aeruginosa serogroup O4 (Lanyi) and related serotype O6 (Habs) and immunotype 1 (Fisher)

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Abstract
Acidic O-specific polysaccharides were isolated on mild acidic degradation of lipopolysaccharides of P. aeruginosa serotypes 04a,b, 04a,c, 04a,d (Lanyi classification) and serologically related to them monosaccharide composition and were built up of L-rhamnose, 2-acetamido-2,6-dideoxy-D-glucose, 2-formamido-2-deoxy-D-galacturonic acid and 2-acetamido-2-deoxy-D-galacturonamide residues. The latter 2 derivatives of D-galactosaminuronic acid were found in nature for the 1st time. All the polysaccharides, but Lanyi serotype 04a,c, contained 0-acetyl groups. The polysaccharides were readily de-0-acetylated with aqueous triethylamine and de-N-formylated with dilute hydrochloric acid. De N-formylated polysaccharide of serotype 04a,c was selectively cleaved with nitrous acid upon 2-amino-2-deoxygalacturonic acid residues to form a tetrasaccharide with a 2,5-anhydrotaluronic acid residue on the reducing end. The tetrasaccharide represented a modified repeating unit of the polysaccharide. Solvolysis of all intact polysaccharides with HF selectively split the glycosidic linkages of 6-deoxy sugars to give the same trisaccharide, including both derivatives of galactosaminuronic acid and having 2-acetamido-2,6-dideoxyglucose on the reducing end. Structural investigation of the oligosaccharides obtained together with methylation analysis and 13C NMR data revealed the following structures of the O-specific polysaccharides. An independent confirmation of the structures of the repeating units was obtained as the result of full interpretation of the 13C NMR spectra of the intact and modified polymers. Spectral data analysis revealed a number of regularities in the effects of glycosidation connecting their values with the anomeric and absolute configuration of pyranose residues. The data on the structures of the O-specific polysaccharides indicated that each of the 5 P. aeruginosa strains under study should be considered as an individual O-serotype within 1 O-serogroup.

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