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The KL26 gene cluster responsible for the synthesis of the K26 capsular polysaccharide (CPS) of Acinetobacter baumannii includes rmlBDAC genes for l-rhamnose (l-Rhap) synthesis, tle to generate 6-deoxy-l-talose (l-6dTalp) from l-Rhap, and a manC gene for D-mannose (D-Manp) that is rare in Acinetobacter CPS. K26 CPS material was isolated from A. baumannii isolate KZ-1098, and studied by sugar analysis, Smith degradation, and one and two-dimensional 1H and 13C NMR spectroscopy before and after O-deacetylation with aqueous ammonia. The following structure of the branched hexasaccharide repeating unit of the CPS was established: →2)-β-D-Manp-1→4-β-D-Glcp-1→3-α-L-6dTalp-1→3-β-D-GlcpNAc-(1→3↑14│Acα-L-Rhap-2←1-α-D-Glcp The structural depolymerase of phage vB_AbaP_APK26 cleaved selectively the β-GlcpNAc-(1→2)-α-Manp linkage in the K26 CPS formed by WzyK26 to give monomer, dimer, and trimer of the CPS repeating unit, which were characterized by high-resolution electrospray ionization mass spectrometry as well as 1H and 13C NMR spectroscopy. The wzyK26 gene responsible for this linkage and the manC gene were only found in six A. baumannii genomes carrying KL26 and one carrying the novel KL148 gene cluster, indicating the rare occurrence of β-GlcpNAc-(1→2)-α-Manp in A. baumannii CPS structures. However, K26 shares a β-d-Glcp-(1→3)-α-l-6dTalp-(1→3)-β-d-GlcpNAc trisaccharide fragment with a group of related A. baumannii CPSs that have varying patterns of acetylation of l-6dTalp.

Acinetobacter baumannii, capsular polysaccharide structure, 6-deoxy-L-talose, depolymerization, A.baumannii, phage depolymerase

NCBI PubMed ID: 34537298
Publication DOI: 10.1016/j.ijbiomac.2021.09.073
Journal NLM ID: 7909578
Publisher: Butterworth-Heinemann
Correspondence: J.J. Kenyon qut.edu.au>
Institutions: N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, M. M. Shemyakin & Y. A. Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia, State Research Center for Applied Microbiology and Biotechnology, Obolensk, Moscow Region, Russia, Centre for Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology. Brisbane, Australia, School of Life and Environmental Sciences, Faculty of Science, University of Sydney, Sydney, Australia
Methods: 13C NMR, 1H NMR, NMR-2D, PCR, sugar analysis, GLC, Smith degradation, de-O-acetylation, HPLC, GPC, bioinformatic analysis, HR-ESI-MS, sequencing, phage characterization, depolymerization by phage