Lipopolysaccharide of Plesiomonas shigelloides O68:H2 (CNCTC 138/92). Expanding the array of P. shigelloides strains with unusual hydrophobic properties of the O-antigens.

The complete structure of lipopolysaccharide from P. shigelloides O68:H2 (strain CNCTC 138/92) has been investigated by NMR spectroscopy, mass spectrometry and chemical methods. It was confirmed that the P. shigelloides O68 O-specific polysaccharide (O-PS) is composed of a trisaccharide repeating-unit (RU) with a new structure: →4)-α-d-Glcp6OAc-(1 → 4)-β-d-GlcpNAcyl3NAc-(1 → 3)-β-FucpNAc4N-(1→ in which a 3-acetamido-2,3-dideoxy-glucosamine was acylated with d-3-hydroxybutyrate. The O-PS is attached to a non-phosphorylated undecasaccharide through →3)-β-d-GlcpNAc-(1 → residue in the outer core region. The inner region comprises the structural element of P. shigelloides core oligosaccharides that resembles these of O17 and O36 serotypes. Glycine linked to the amine group of the→6)-α-d-GlcpN-(1 → and an α-Kdo-(1 → residue at the position 4 of →5)-α-Kdo-(1 → were identified. The lipid A of the O68 LPS comprises β-d-GlcpN4P-(1 → 6)-α-d-GlcpN1P disaccharide acylated with 14:0(3-OH), 12:0(3-OH), 14:0(3-O-14:0) and 12:0(3-O-12:0) at C-2, C-3, C-2' and C-3'. The presence of O-, N-acetyls and d-3-hydroxybutyryl makes the P. shigelloides O68 O-PS more hydrophobic than typical enterobacterial O-antigen. This finding expands the array of P. shigelloides strains with the phenol-soluble S-type LPS. Immunochemical studies confirmed unique features of the O-PS.