Correlation of Acinetobacter baumannii K144 and K86 capsular polysaccharide structures with genes at the K locus reveals the involvement of a novel multifunctional rhamnosyltransferase for structural synthesis

Int J Biol Macromol. 2021 Dec 15;193(Pt B):1294-1300. doi: 10.1016/j.ijbiomac.2021.10.178. Epub 2021 Oct 30.


Whole genome sequence from Acinetobacter baumannii isolate Ab-46-1632 reveals a novel KL144 capsular polysaccharide (CPS) biosynthesis gene cluster, which carries genes for d-glucuronic acid (D-GlcA) and l-rhamnose (l-Rha) synthesis. The CPS was extracted from Ab-46-1632 and studied by 1H and 13C NMR spectroscopy, including a two-dimensional 1H,13C HMBC experiment and Smith degradation. The CPS was found to have a hexasaccharide repeat unit composed of four l-Rhap residues and one residue each of d-GlcpA and N-acetyl-d-glucosamine (D-GlcpNAc) consistent with sugar synthesis genes present in KL144. The K144 CPS structure was established and found to be related to those of A. baumannii K55, K74, K85, and K86. A comparison of the corresponding gene clusters to KL144 revealed a number of shared glycosyltransferase genes correlating to shared glycosidic linkages in the structures. One from the enzymes, encoded by only KL144 and KL86, is proposed to be a novel multifunctional rhamnosyltransfaerase likely responsible for synthesis of a shared α-l-Rhap-(1 → 2)-α-L-Rhap-(1 → 3)-L-Rhap trisaccharide fragment in the K144 and K86 structures.

Keywords: Acinetobacter baumannii; Capsular polysaccharide; K144; K86; Multifunctional glycosyltransferase.

MeSH terms

  • Acinetobacter baumannii / genetics*
  • Bacterial Proteins / genetics*
  • Genetic Linkage / genetics
  • Glycosyltransferases / genetics
  • Magnetic Resonance Spectroscopy / methods
  • Multigene Family / genetics
  • Polysaccharides, Bacterial / genetics*
  • Whole Genome Sequencing / methods


  • Bacterial Proteins
  • Polysaccharides, Bacterial
  • Glycosyltransferases