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Elucidation of the K32 Capsular Polysaccharide Structure and Characterization of the KL32 Gene Cluster of Acinetobacter baumannii LUH5549

S. M. Cahill1, N. P. Arbatsky2, A. S. Shashkov2, M. M. Shneider3, A. V. Popova4,5, R. M. Hall6#, J. J. Kenyon1#, and Y. A. Knirel2,a*#

1Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, QLD 4001 Brisbane, Australia

2Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Moscow, Russia

3Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 117997 Moscow, Russia

4Moscow Institute of Physics and Technology, 141701 Dolgoprudny, Moscow Region, Russia

5State Research Center for Applied Microbiology and Biotechnology, 142279 Obolensk, Moscow Region, Russia

6School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia

# These authors contributed equally to this work.

* To whom correspondence should be addressed.

Received October 29, 2019; Revised November 20, 2019; Accepted November 26, 2019
Capsular polysaccharide (CPS), isolated from Acinetobacter baumannii LUH5549 carrying the KL32 capsule biosynthesis gene cluster, was studied by sugar analysis, Smith degradation, and one- and two-dimensional 1H and 13C NMR spectroscopy. The K32 CPS was found to be composed of branched pentasaccharide repeats (K units) containing two residues of β-D-GalpNAc and one residue of β-D-GlcpA (β-D-glucuronic acid) in the main chain and one residue each of β-D-Glcp and α-D-GlcpNAc in the disaccharide side chain. Consistent with the established CPS structure, the KL32 gene cluster includes genes for a UDP-glucose 6-dehydrogenase (Ugd3) responsible for D-GlcA synthesis and four glycosyltransferases that were assigned to specific linkages. Genes encoding an acetyltransferase and an unknown protein product were not involved in CPS biosynthesis. Whilst the KL32 gene cluster has previously been found in the global clone 2 (GC2) lineage, LUH5549 belongs to the sequence type ST354, thus demonstrating horizontal gene transfer between these lineages.
KEY WORDS: Acinetobacter baumannii, capsule, K locus, polysaccharide structure, glucuronic acid

DOI: 10.1134/S000629792002011X