Structural studies of the O-antigen isolated from the phenol-soluble lipopolysaccharide of Acinetobacter baumannii (DNA group 2) strain 9.

A polysaccharide containing D-GalNAc, D-Glc and 4-acetamido-4,6-dideoxy-D-glucose (Qui4NAc) was isolated from the phenol-soluble lipopolysaccharide originating from Acinetobacter baumannii strain 9. The structure of the repeating unit was shown by means of monosaccharide analyses, Smith-degradation, partial acid hydrolysis, mass spectrometry, and NMR spectroscopy to be a branched pentasaccharide, in which the tetrasaccharide backbone is built from amino sugars only. [structure: see text] The polysaccharide was identified by serological and western blot analyses as the O-antigen of the lipopolysaccharide.