Structure elucidation of the capsular polysaccharide of Acinetobacter baumannii AB5075 having the KL25 capsule biosynthesis locus

•Capsular polysaccharide was isolated from Acinetobacter baumannii AB5075•Structure of the polysaccharide was established by NMR and chemical approaches•Capsule biosynthesis locus was analyzed and found to match the structure established

Capsular polysaccharide was isolated by the phenol–water extraction of Acinetobacter baumannii AB5075 and studied by 1D and 2D 1H and 13C NMR spectroscopy. The following structure of the linear trisaccharide repeating unit was established:→3)-β-d-ManpNAcA-(1→4)-β-d-ManpNAcA-(1→3)-α-d-QuipNAc4NR-(1→where R indicates (S)-3-hydroxybutanoyl or acetyl in the ratio∼2.5:1. The genes in the polysaccharide biosynthesis locus designated KL25 are appropriate to the established CPS structure.

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