Structure of the O-specific polysaccharide of Aeromonas veronii bv. sobria strain Pt393 isolated from rainbow trout (Oncorhynchus mykiss), which contains a rarely occurring sugar 4-acetamido-4,6-dideoxy-D-galactose, tomosamine

Abstract The O-specific polysaccharide (OPS) was isolated from the lipopolysaccharide of Aeromonas veronii bv. sobria strain Pt393, which is pathogenic to the rainbow trout (Oncorhynchus mykiss), after mild acid hydrolysis followed by GPC. The high-molecular-weight OPS fraction was studied with chemical methods, mass spectrometry, and 1H and 13C NMR spectroscopy techniques, including 2D 1H,1H COSY, TOCSY, NOESY, 1H-detected heteronuclear 1H,13C HSQC, and HMBC experiments. It was found that the O-specific polysaccharide was built of a tetrasaccharide repeating unit composed of α-GalpNAc, α-FucpNAc, β-QuipNAc, and α-Fucp4NAc (4-acetamido-4,6-dideoxy- d -galactose, tomosamine) residues. The following structure of the OPS of A. sobria strain Pt393 was established: →4)-α-D-GalpNAc-(1 → 3)-α- L- FucpNAc-(1 → 3)-β- D- QuipNAc-(1 → 3)-α- D- Fucp4NAc-(1→