Structural and genetic relatedness of the O-antigens of Escherichia coli O50 and O2

• Published in: Carbohydrate research 2018-07, Vol.464, p.8-11
• Main Authors: Yang, Bin, Senchenkova, Sof'ya N., Naumenko, Olesya I., Shashkov, Alexander S., Liu, Bin, Perepelov, Andrey V., Knirel, Yuriy A.
• Format: Article
• Language: English
• Subjects: Bacterial polysaccharide structure; Escherichia coli; Lipopolysaccharide; O-antigen; O-antigen gene cluster; O-specific polysaccharide
• ISSN: 0008-6215; 1873-426X
• DOI: 10.1016/j.carres.2018.05.001

An O-specific polysaccharide (O-antigen) was isolated by mild acid degradation of the lipopolysaccharide of Escherichia coli O50 followed by gel chromatography on Sephadex G-50. The following structure of the tetrasaccharide repeat was established by sugar analysis and 1D and 2D 1H and 13C NMR spectroscopy: →3)-α-l-Rhap-(1 → 2)-α-l-Rhap-(1 → 3)-β-l-Rhap-(1 → 4)-β-d-GlcpNAc-(1→ The linear O50 polysaccharide has the same structure as the main chain of the branched O polysaccharide of E. coli O2 studied earlier [Jansson et al., Carbohydr. Res. 161 (1987) 273–279], which differs in the presence of a side-chain α-d-Fucp3NAc residue. In spite of the difference between the O-polysaccharides, the corresponding genes in the O2- and O50-antigen gene cluster are 99–100% identical. The genetic basis for the lack of d-Fucp3NAc from the O50 polysaccharide is evidently a point mutation in the aminotransferase gene fdtB of the d-Fucp3NAc synthesis pathway resulting in a single amino acid change from histidine in O2 to arginine in O50. [Display omitted] •E. coli is the predominant facultative anaerobe of the colonic flora of mammals.•The O-polysaccharide structure of E. coli O50 was established.•The OPS has the same main chain of the branched O-polysaccharide of E. coli O2.•The O-antigen gene cluster of E. coli O50 was sequenced and annotated.•Genetic basis for the lack of Fuc3NAc is a point mutation.