— The data on the structure of O-specific polysaccharides (O-antigens) of all nine known molecular types (potential O-serotypes) of a new type of enterobacteria Escherichia albertii , causative agents of intestinal infections in humans and birds, are presented. The advantages and limitations of structural analysis methods used to determine the structure of E. albertii polysaccharides are discussed. The annotation of genes in gene clusters of biosynthesis of O-antigens of E. albertii was carried out by comparison with the sequences in the available databases. Structural and genetic relationships between O-antigens of E. albertii and closely related species of E. coli are discussed. It was found that, in addition to the O-antigen, E. albertii O9 expresses a mannan of the same structure as the mannan of E. coli O8.

Several types of Escherichia coli O-antigens form highly effective shields protecting the bacterial cell surface and preventing bacteriophages from interacting directly with their secondary (terminal) receptors. However, it is not clear if O-antigens of various types (O-serotypes) differ in their anti-phage protection efficacy. Here, we describe a new E. coli strain, F5, which has an E. coli O28ab-related O-antigen. Although the amount of O-antigen produced by this strain is comparable to that produced by other E. coli strains we tested, it appears to give the cells significantly lower protection against phage attack than other O-antigen types, such as the O-polysaccharide of E. coli F17, which we studied earlier.

Structure of the O-polysaccharide (O-antigen) of Escherichia coli O60 was studied by sugar analysis, partial solvolysis with CF3CO2H, and 1D and 2D 1H and 13C NMR spectroscopy. The O-polysaccharide was found to consist of D-galactose and L-rhamnose. The structure of its branched tetrasaccharide repeating unit was established, which is unique among known bacterial polysaccharide structures.

This corrects the article DOI: 10.1134/S0006297916060067.

Gene clusters for biosynthesis of 24 of 34 basic O-antigen forms of Shigella spp. are identical or similar to those of the genetically closely related bacterium Escherichia coli. For 18 of these relatedness was confirmed chemically by elucidation of the O-antigen (O-polysaccharide) structures. In this work, structures of the six remaining O-antigens of E. coli O32, O53, O79, O105, O183 (all related to S. boydii serotypes), and O38 (related to S. dysenteriae type 8) were established using 1H and 13C NMR spectroscopy. They were found to be identical to the Shigella counterparts, except for the O32- and O38-polysaccharides, which differ in the presence of O-acetyl groups. The structure of the E. coli O105-related O-polysaccharide of S. boydii type 11 proposed earlier is revised. The contents of the O-antigen gene clusters of the related strains of E. coli and Shigella spp. and different mechanisms of O-antigen diversification in these bacteria are discussed in view of the O-polysaccharide structures established. These data illustrate the value of the O-antigen chemistry and genetics for elucidation of evolutionary relationships of bacteria.

O-Polysaccharides (O-antigens) of a number of genetically related Escherichia coli O-serogroups (O17, O44, O73, O77, and O106) and Salmonella enterica O:6,14 possess an identical main chain composed of d-GlcNAc and d-Man residues and differ from each other by the absence or presence of glucose side chains at various positions. Using two-dimensional NMR spectroscopy, we established the structure of the O-polysaccharide of E. coli O106 having two glucose side chains in a hexasaccharide repeating unit.