Abstract
Acinetobacter baumannii is a significant nosocomial pathogen characterized by the ability to produce a wide variety of capsular polysaccharides (CPSs). The structures of a K102-type CPS isolated from A. baumannii KZ-1102 and its Smith degradation product were determined by sugar analysis, 1D and 2D (1)H NMR spectroscopy, and (13)C NMR spectroscopy. The K102 CPS biosynthesis gene cluster (KL102) contains genes for common sugar synthesis, K unit processing, capsule export, glycosyl transfer, initiating sugar phosphate transfer, and genes that encode d-GlcpNAc/d-GalpNAc dehydrogenase and phosphoglycerol transferase. The CPS is composed of a pentasaccharide repeating unit (K unit) consisting of a tetrasaccharide backbone including one α-d-Galp, three α-d-GlcpNAc residues, and one residue of a β-d-Glcp as a side chain. The tailspike depolymerase of the specific Obolenskvirus phage Cato was found to cleave the α-d-GlcpNAc-(1→6)-α-d-GlcpNAc linkage in the K102 CPS to give the monomer and dimer of the K repeating unit, which were characterized by high-resolution electrospray ionization mass spectrometry as well as (1)H and (13)C NMR spectroscopy.