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Capsular polysaccharides (CPSs), from Acinetobacter baumannii isolates 1432, 4190 and NIPH 70, which have related gene content at the K locus, were examined, and the chemical structures established using 2D(1)H and(13)C NMR spectroscopy. The three isolates produce the same pentasaccharide repeat unit, which consists of 5-N-acetyl-7-N-[(S)-3-hydroxybutanoyl] (major) or 5,7-di-N-acetyl (minor) derivatives of 5,7-diamino-3,5,7,9-tetradeoxy-D-glycero-D-galacto-non-2-ulosonic (legionaminic) acid (Leg5Ac7R), D-galactose, N-acetyl-D-galactosamine and N-acetyl-D-glucosamine. However, the linkage between repeat units in NIPH 70 was different to that in 1432 and 4190, and this significantly alters the CPS structure. The KL27 gene cluster in 4190 and KL44 gene cluster in NIPH 70 are organized identically and contain lga genes for Leg5Ac7R synthesis, genes for the synthesis of the common sugars, as well as anitrA2 initiating transferase and four glycosyltransferases genes. They share high-level nucleotide sequence identity for corresponding genes, but differ in the wzy gene encoding the Wzy polymerase. The Wzy proteins, which have different lengths and share no similarity, would form the unrelated linkages in the K27 and K44 structures. The linkages formed by the four shared glycosyltransferases were predicted by comparison with gene clusters that synthesize related structures. These findings unambiguously identify the linkages formed by WzyK27 and WzyK44, and show that the presence of different wzy genes in otherwise closely related K gene clusters changes the structure of the CPS. This may affect its capacity as a protective barrier for A. baumannii.

Acinetobacter baumannii, capsular polysaccharide, gene cluster, legionaminic acid, Wzy polymerase, K locus

NCBI PubMed ID: 26711304
Publication DOI: 10.1093/glycob/cwv168
Journal NLM ID: 9104124
Publisher: IRL Press at Oxford University Press
Correspondence: johanna.kenyon

qut.edu.au
Institutions: Russian Academy of Sciences, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, School of Molecular Bioscience, The University of Sydney, Sydney, Australia School of Biomedical Sciences, Queensland University of Technology, Brisbane, Australia, Russian Academy of Sciences, M. M. Shemyakin & Y. A. Ovchinnikov Institute of Bioorganic Chemistry, Moscow, Russia, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow, Russia State Research Center for Applied Microbiology and Biotechnology, Obolensk, Moscow, Russia
Methods: 13C NMR, 1H NMR, NMR-2D, PCR, DNA sequencing, sugar analysis, DNA techniques, ESI-MS, acid hydrolysis, GLC, mild acid hydrolysis, GPC, function analysis of gene clusters