Structure of the Acidic Polysaccharide Chain of the Lipopolysaccharide of Shewanella Alga 48055

A lipopolysaccharide (LPS) with an acidic polysaccharide chain was isolated from the bacterium Shewanella alga strain 48055 and cleaved selectively at the glycosidic linkage of N-acetylneuraminic acid to give a tetrasaccharide. Studies of the tetrasaccharide and the O-deacylated LPS by 1H and 13C NMR spectroscopy, including 2D COSY, TOCSY, NOESY, rotating-frame NOE spectroscopy (ROESY), and H-detected 1H, 13C heteronuclear multiple-quantum coherence (HMQC) experiments, revealed the following structure of the polysaccharide repeating unit: -->3)-beta-D-GalpA6GroN-(1-->3)-beta-D-GlcpNAc-(1-->3)-alpha-D- GalpA6GroN- (1-->4)-alpha-Neup5Ac-(2--> where GroN is an amidically linked residue of 2-amino-1,3-propanediol (2-amino-2-deoxyglycerol). A similar structure, but with 2-acetamido-2,6-dideoxy-D-glucose instead of 2-acetamido-2-deoxy-D-glucose, has been reported previously for the polysaccharide chain of a non-O1 Vibrio cholerae H11 LPS [E. V. Vinogradov, O. Holst, J.E. Thomas-Oates, K.W. Broady, and H. Brade, Eur. J. Biochem., 210 (1992) 491-498].