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. α‐ D‐Glcp 1 ∣ 6 ←3)‐β‐ D‐Quip4NAc‐(1←3)‐α‐ D‐GalpNAc‐(1←4)‐α‐ D‐GalpNAc‐(1←3)‐α‐ D‐GalpNAc‐(1← The polysaccharide was identified by serological and western blot analyses as the O‐antigen of the lipopolysaccharide.