Structure of a colitose-containing O-specific polysaccharide of the marine bacterium Pseudoalteromonas tetraodonis IAM 14160^T

O-specific polysaccharide was isolated by mild acid degradation of the lipopolysaccharide of Pseudoalteromonas tetraodonis type strain IAM 14160^T and studied by sugar and methylation analyses along with ¹H and ¹³C NMR spectroscopy, including 2D COSY, TOCSY, ¹H,¹³C HMQC and HMBC experiments. The polysaccharide was found to consist of hexasaccharide repeating units containing one residue each of D-Gal, D-GlcA, D-GalNAc and D-GlcNAc and two residues of 3,6-dideoxy-L-xylo-hexose (colitose, Col) and having the following structure: →2)-α-Colp-(1→4)-β-D-GlcpNac-(1→4)-β-D-GlcpA- (1→3)-β-D-GalpNac-(1→ 3 ↑ α-Colp-(1→2)-β-D-Galp. In common with the polysaccharides of some other bacteria, the polysaccharide studied contains a tetrasaccharide fragment α-Colp-(1 → 2)-β-D-Galp-(1 → 3)-[α-Colp-(1 → 4)]-β-D-GlcpNAc, which is a colitose ('3-deoxy-L-fucose') analogue of the Lewis^b blood group antigenic determinant.