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The K8 and K54 capsular polysaccharides were isolated from Acinetobacter baumannii BAL 097 and RCH52, respectively, and studied by sugar analysis, partial acid hydrolysis and selective solvolysis with CF3CO2H in the presence of 2-methyl-1-propanol, along with 1D and 2D 1H and 13C NMR spectroscopy. The following structures of related branched tetrasaccharide repeats (K units) of the polysaccharides were established: [structure: see text] where Leg indicates 5,7-diamino-3,5,7,9-tetradeoxy-d-glycero-d-galacto-non-2-ulosonic (legionaminic) acid and R indicates (R)-3-hydroxybutanoyl or acetyl in the ratio ~2.5:1. The sequences of the KL8 and KL54 capsule gene clusters were closely related. The difference in the acyl group at O-7 on the sidechain legionaminic acid is due to differences in two genes in the legionaminic acid biosynthesis cluster. The wzy genes encoding the K unit polymerases are also different and make different linkages between the K units, allowing the first sugar of both K units to be identified as d-GlcpNAc. The shared Gtr20 glycosyltransferase, also encoded in KL63, forms the α-l-FucpNAc-(1→3)-d-GlcpNAc linkage, and Gtr19 was predicted to form α-d-GalpNAc-(1→3)-l-FucpNAc. Gtr18 from KL8 is 75% identical to Gtr108 from KL54 and both would link the Leg derivative to d-GalpNAc. Hence the genes present at the K locus were consistent with the composition and structures of the K8 and K54 capsular polysaccharides.

capsular polysaccharide, Acinetobacter baumannii, legionaminic acid, selective cleavage, K locus, K unit

NCBI PubMed ID: 31349142
Publication DOI: 10.1016/j.carres.2019.107745
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: J.J. Kenyon
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, Moscow Institute of Physics and Technology, Dolgoprudny, Moscow Region, Russia, Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia, Higher Chemical College of the Russian Academy of Sciences, D. I. Mendeleev University of Chemical Technology of Russia, Moscow, Russia
Methods: 13C NMR, 1H NMR, NMR-2D, partial acid hydrolysis, sugar analysis, ESI-MS, GLC, GPC, UV, bioinformatic analysis, solvolysis with anhydrous trifluoroacetic acid

Bacterial extracellular polysaccharides are known as a cell-bound capsule, a sheath, or a slime, which is excreted into the environment. They play an important role in virulence of medical bacteria and plant-to-symbiont interaction and are used for serotyping of bacteria and production of vaccines. Some exopolysaccharides have commercial applications in industry, and claims of health benefits have been documented for an increasing number of them. Exopolysaccharides have diverse composition and structure, and some contain sugar and non-sugar components that are found in bacterial carbohydrates only. The present article provides an updated collection of the data on exopolysaccharides of various classes of gram-negative and gram-positive bacteria reported until the end of 2019. When known, biosynthesis pathways of exopolysaccharides are treated in a summary manner. References are made to structure and biosynthesis relatedness between exopolysaccharides of different bacterial taxa as well as between bacterial polysaccharides and mammalian glycosaminoglycans.

polysaccharide structure, Gram-negative bacteria, capsule, Biofilm, polysaccharide biosynthesis, gram-positive bacteria, Monosaccharide composition, Bacterial exopolysaccharide, non-sugar component

Publication DOI: 10.1016/B978-0-12-819475-1.00005-5
Publisher: Elsevier
Correspondence: marie-rose.vancalsteren@canada.ca; yknirel@gmail.com
Editors: Barchi J, Kamerling H
Institutions: N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, Saint-Hyacinthe Research and Development Centre, Agriculture and Agri-Food Canada, Saint-Hyacinthe, QC, Canada

The polysaccharide capsule surrounding bacterial cell plays an important role in pathogenesis of infections caused by the opportunistic pathogen Acinetobacter baumannii by providing protection from external factors. The structures of the capsular polysaccharide (CPS) produced by A. baumannii isolates and the corresponding CPS biosynthesis gene clusters are highly diverse, although many of them are related. Many types of A. baumannii CPSs contain isomers of 5,7-diamino-3,5,7,9-tetradeoxynon-2-ulosonic acid (DTNA). Three of these isomers, namely acinetaminic acid (l-glycero-l-altro isomer), 8-epiacinetaminic acid (d-glycero-l-altro isomer), and 8-epipseudaminic acid (d-glycero-l-manno isomer), have not been found so far in naturally occurring carbohydrates from other species. In A. baumannii CPSs, DTNAs carry N-acyl substituents at positions 5 and 7; in some CPSs, both N-acetyl and N-(3-hydroxybutanoyl) groups are present. Remarkably, pseudaminic acid carries the (R)-isomer and legionaminic acid carries the (S)-isomer of the 3-hydroxybutanoyl group. The review addresses the structure and genetics of biosynthesis of A. baumannii CPSs containing di-N-acyl derivatives of DTNA.

capsular polysaccharide, Acinetobacter baumannii, nonulosonic acid, Bacterial polysaccharide, capsule, higher monosaccharide, acyl group

NCBI PubMed ID: 37072328
Publication DOI: 10.1134/S0006297923020049
Journal NLM ID: 0376536
Publisher: Nauka/Interperiodica
Correspondence: Y.A. Knirel
Institutions: State Research Center for Applied Microbiology and Biotechnology, Obolensk, Moscow Region, 142279, Russia, Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, 117913, Russia, Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997, Russia, Branch of the Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry in Pushchino, Russian Academy of Sciences, Pushchino, Moscow Region, 142290, Russia