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Nonulosonic acids are found in the surface polysaccharides of many bacterial species and are often implicated in pathogenesis. Here, the structure of a novel 5,7-diacetamido-3,5,7,9-tetradeoxynon-2-ulosonic acid recovered from the capsular polysaccharide of a multiply antibiotic resistant Acinetobacter baumannii isolate was determined. The isolate carries a sugar synthesis module that differs by only a single gene from the module for the synthesis of 5,7-diacetamido-3,5,7,9-tetradeoxy-L-glycero-L-altro-non-2-ulosonic acid or 5,7-di-N-acetylacinetaminic acid, recently discovered in the capsule of another A. baumannii isolate. The new monosaccharide is the C8-epimer of acinetaminic acid (8eAci; 5,7-diacetamido-3,5,7,9-tetradeoxy-D-glycero-L-altro-non-2-ulosonic acid) and the C7-epimer of legionaminic acid. This monosaccharide had not previously been detected in a biological sample but had been synthesized chemically.

structure, Acinetobacter baumannii, capsular polysaccharide, nonulosonic acid, 5, 7, 7-diacetamido-3, legionaminic acid, capsule, surface polysaccharide, 7-Di-N-acetyl-8-epiacinetaminic acid, 9-tetradeoxy-D-glycero-L-altro-non-2-ulosonic acid

NCBI PubMed ID: 28900250
Publication DOI: 10.1038/s41598-017-11166-4
Journal NLM ID: 101563288
Publisher: London: Nature Publishing Group
Correspondence: decastro@unina.it; ruth.hall@sydney.edu.au
Institutions: Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia, School of Life and Environmental Sciences, The University of Sydney, Sydney, Australia, Department of Chemical Sciences, University of Napoli, Naples, Italy, Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore, Department of Infectious Diseases, Tan Tock Seng Hospital, Singapore, Singapore, Department of Agricultural Sciences, University of Napoli, Naples, Italy
Methods: 13C NMR, 1H NMR, methylation, NMR-2D, DNA sequencing, GC-MS, enzymatic hydrolysis, mild acid hydrolysis, composition analysis, bioinformatic analysis, SEC

Structures of capsular polysaccharides of Acinetobacter baumannii isolates carrying KL13 and KL73 gene clusters were established. The closely related KL73 and KL13 gene clusters differ only by one gene in the module responsible for synthesis of the non-2-ulosonic acids. The K13 and K73 polysaccharides differ only in a single side-chain sugar, which is either 5,7-diacetamido-3,5,7,9-tetradeoxy-l-glycero-l-altro- or -d-glycero-l-altro-non-2-ulosonic acid [di-N-acetylated forms of acinetaminic acid (Aci5Ac7Ac) or 8-epiacinetaminic acid (8eAci5Ac7Ac), respectively]. The KL13 also is closely related to the KL12 gene cluster, which contains a different wzy gene encoding the K unit polymerase. Accordingly, the otherwise near identical K units are linked differently via an α-d-FucpNAc-(1→4)-d-Galp linkage in K13 and K73 or an α-d-FucpNAc-(1→3)-d-GalpNAc linkage in K12. This finding confirms the predicted substrate of the ItrB3 initiating transferase as d-FucpNAc. Glycosyltransferases predicted to catalyse the linkage of d-Galp or d-GalpNAc to l-FucpNAc in the growing K13 and K73 or K12 units, respectively, differ by only two amino acids.

Acinetobacter baumannii, capsular polysaccharide, capsular polysaccharide structure, 5, 7-Di-N-acetyl-8-epiacinetaminic acid, Capsule biosynthesis gene cluster, Non-2-ulosonic acid 5, 7-Di-N-acetylacinetaminic acid

NCBI PubMed ID: 29100177
Publication DOI: 10.1016/j.carres.2017.10.005
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: decastro@unina.it; ruth.hall@sydney.edu.au
Institutions: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, Institute of Health and Biomedical Innovation, 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, Department of Chemical Sciences, University of Naples, Naples, Italy, Department of Agricultural Sciences, University of Naples, Naples, Italy

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.

Acinetobacter baumannii, capsular polysaccharide, 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