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Enterotoxigenic Escherichia coli are causative agents of diarrhea in humans as well as animals, and E.coli O170 belongs to this virotype. Upon mild acid degradation of the lipopolysaccharide of E.coli O170, the branched O-polysaccharide chain was partially cleaved at ?-d-glactofuranosidic linkages to give multiple products, including a linear tetrasaccharide and oligomers thereof. Studies of the acid degradation products and O-deacylated lipopolysaccharide by 1D and 2D 1H and 13C NMR spectroscopy enabled elucidation of the following O-polysaccharide structure: Functions of genes in the O-antigen biosynthesis gene cluster were tentatively assigned and found to be in agreement with the O-polysaccharide structure.

Lipopolysaccharide, Escherichia coli, O-polysaccharide, bacterial polysaccharide structure, O-antigen gene cluster

NCBI PubMed ID: 26382081
Publication DOI: 10.1016/j.carres.2015.08.013
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: perepel@ioc.ac.ru (A.V. Perepelov)
Institutions: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, TEDA School of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, China, Department of Laboratory Medicine, Division of Clinical Microbiology, Karolinska Institute, Karolinska University Hospital, Stockholm, Sweden
Methods: 13C NMR, 1H NMR, NMR-2D, de-O-acylation, sugar analysis, acid hydrolysis, GLC, mild acid hydrolysis, NMR-1D, GPC

Mild acid degradation of the lipopolysaccharide of Escherichia coli O96 afforded a mixture of two polysaccharides. The following structure of the pentasaccharide repeating unit of the major polymer was established by sugar analysis, Smith degradation, and (1)H and (13)C NMR spectroscopy: [Formula: see text]. The O-antigen gene cluster of E. coli O96 between conserved galF and gnd genes was found to be consistent with this structure, and hence, the major polysaccharide represents the O96-antigen. The O96-antigen structure and gene cluster are similar to those of E. coli O170, and two proteins encoded in the gene clusters of both bacteria were putatively assigned a function of galactofuranosyltransferases. The minor polymer has the same structure as a peptidoglycan-related polysaccharide reported earlier in Providencia alcalifeciens O45 and several other O-serogoups of this species (Ovchinnikova OG, Liu B, Kocharova NA, Shashkov AS, Kondakova AN, Siwinska M, Feng L, Rozalski A, Wang L, Knirel YA. Biochemistry (Moscow) 2012;77:609-15) →4)-β-D-GlcpNAc-(1→4)-β-D-GlcpNAc3(Rlac-lAla)-(1→ where Rlac-lAla indicates (R)-1-[(S)-1-carboxyethylaminocarbonyl]ethyl.

O-antigen, Escherichia coli, O-polysaccharide, bacterial polysaccharide structure, O-antigen gene cluster, Peptidoglycan-related polysaccharide

NCBI PubMed ID: 26706815
Publication DOI: 10.1016/j.carres.2015.11.005
Journal NLM ID: 0043535
Publisher: Elsevier
Correspondence: perepel@ioc.ac.ru
Institutions: N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, China
Methods: 13C NMR, 1H NMR, NMR-2D, sugar analysis, ESI-MS, acid hydrolysis, GLC, Smith degradation, GPC, mild acid degradation, function analysis of gene clusters

This review is devoted to methods for the selective cleavage of glycosidic bonds. The mechanisms of reactions underlying these methods are considered and examples of their practical application in the structural analysis of bacterial polysaccharides are given. Specific methods for the selective cleavage of polysaccharides, remaining relevant for researchers, include the Smith degradation based on destruction of monosaccharides containing vicinal diol groups, dephosphorylation of phosphate-containing polysaccharides with hydrofluoric acid and the hydrolytic cleavage of glycosyl phosphate bonds in the latter compounds. Non-specific methods, including partial acid hydrolysis, acetolysis and solvolysis with anhydrous organic (CF3SO3H, MeSO3H, CF3CO2H) and inorganic (HF) acids do not make any specific demands on the composition and structure of the polysaccharide and are sensitive to its fine structural features. The review addesses the issue of stability of glycosidic bonds in various monosaccharides to reagents used for non-specific selective cleavage.

structural analysis, Bacterial polysaccharide, selective cleavage, glycosidic bond

Publication DOI: 10.1070/RCR4856
Journal NLM ID: 0404506
Publisher: London: Chemical Society
Correspondence: Yu.A. Knirel
Institutions: N.D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences
Methods: partial acid hydrolysis, HF solvolysis, acid hydrolysis, mild acid hydrolysis, alkaline degradation, b-elimination, Smith degradation, deamination, de-O-acetylation, HF treatment, reduction with NaBD4, triflic acid solvolysis, acetolysis, Li/ethylenediamine degradation, hydrazinolysis, reduction with NaBH4, mild acid degradation, trifluoroacetic acid solvolysis, partial solvolysis with anhydrous trifluoroacetic acid, de-N-acetylation with hydrazine, part acid hydrolysis, HF solvolysis; published polymerization frame was shifted for conformity with other records.

Escherichia coli includes clonal groups of both commensal and pathogenic strains, with some of the latter causing serious infectious diseases. O antigen variation is current standard in defining strains for taxonomy and epidemiology, providing the basis for many serotyping schemes for Gram-negative bacteria. This review covers the diversity in E. coli O antigen structures and gene clusters, and the genetic basis for the structural diversity. Of the 187 formally defined O antigens, six (O31, O47, O67, O72, O94 and O122) have since been removed and four (O14, O34, O89 and O144) strains do not produce any O antigen. Therefore, structures are presented for 176 of the 181 E. coli O antigens, some of which include subgroups. Most (93%) of these O antigens are synthesized via the Wzx/Wzy pathway, 11 via the ABC transporter pathway, with O20, O57 and O60 still uncharacterized due to failure to find their O antigen gene clusters. Biosynthetic pathways are given for 38 of the 49 sugars found in E. coli O antigens, and several pairs or groups of the E. coli antigens that have related structures show close relationships of the O antigen gene clusters within clades, thereby highlighting the genetic basis of the evolution of diversity.

structure, O antigen, Escherichia coli, gene cluster, serogroup, diversity

NCBI PubMed ID: 31778182
Publication DOI: 10.1093/femsre/fuz028
Journal NLM ID: 8902526
Publisher: Oxford University Press
Correspondence: G. Widmalm ; Lei Wang
Institutions: Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden, N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow, Russia, Tianjin Key Laboratory of Microbial Functional Genomics, Tianjin, China, The Key Laboratory of Molecular Microbiology and Technology, Ministry of Education, Tianjin, China, School of Molecular and Microbial Bioscience (G08), University of Sydney, Sydney, Australia, TEDA Institute of Biological Sciences and Biotechnology, Nankai University, TEDA, Tianjin, China, Department of Immunology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin, China