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The structure of the K141 type capsular polysaccharide (CPS) produced by Acinetobacter baumannii KZ1106, a clinical isolate recovered from Kazakhstan in 2016, was established by sugar analyses and one- and two-dimensional 1H and 13C NMR spectroscopy. The CPS was shown to consist of branched tetrasaccharide repeating units (K-units) with the following structure: [Display omitted] This structure was found to be consistent with the genetic content of the KL141 CPS biosynthesis gene cluster at the chromosomal K locus in the KZ1106 whole genome sequence. Assignment of the encoded enzymes allowed the first sugar of the K unit to be identified, which revealed that the β-d-Glc p NAc-(1→3)-d-Glc p NAc bond is the linkage between K-units formed by the Wzy KL141 polymerase. [Display omitted] • Complete structure of Acinetobacter baumannii K141 CPS solved. • Annotations for the KL141 gene cluster reported. • Genetic content of KL141 is consistent with the structure reported. [ABSTRACT FROM AUTHOR]

The structure of the K128 capsular polysaccharide (CPS) produced by Acinetobacter baumannii isolate KZ-1093 from Kazakhstan was established by sugar analysis and Smith degradation along with 1D and 2D 1H and 13C NMR spectroscopy. The CPS was found to consist of branched pentasaccharide repeating units containing only neutral sugars, and its composition and topology are closely related to those of the A. baumannii K116 CPS. The K128 and K116 oligosaccharide units differ in the linkage between the disaccharide side chain and the main chain, with a β-(1 → 6) linkage in K128 replacing a β-(1 → 4) linkage in K116. The linkages between the repeating units in the K128 and K116 CPSs are also different, with K128 units linked by β- d -Gal p NAc-(1 → 4)- d -Gal p, and β- d -Gal p NAc-(1 → 3)- d -Gal p linkages between K116 units. The KZ-1093 genome was sequenced and the CPS biosynthesis gene cluster at the chromosomal K locus was designated KL128. Consistent with the CPS structures, KL128 differs from KL116 in one glycosyltransferase gene and the gene for the Wzy polymerase. In KL128, the gtr200 glycosyltransferase gene replaces gtr76 in KL116, and Gtr200 was therefore assigned to the different β- d -Gal p NAc-(1 → 6)- d -Gal p linkage in K128. Similarly, the Wzy K128 polymerase could be assigned to the β- d -Gal p NAc-(1 → 4)- d -Gal p linkage between the K128 units. Image 1 • The Acinetobacter baumannii K128 capsule structure is closely related to the K116 capsule structure. • The function of the glycosyltransferases, Wzy polymerases and initiating transferase were unambiguously assigned. • The KL128 gene cluster includes genes for glycosyltransferases and simple sugar synthesis. [ABSTRACT FROM AUTHOR]