Structures and gene clusters of the closely related O-antigens of Escherichia coli O46 and O134, both containing d-glucuronoyl-d-allothreonine

•Structures of the O-antigens of Escherichia coli O46 and O134 were elucidated.•d-Allothreonine is linked as an amide to glucuronic acid.•The O-antigens of the two strains differ only in the pattern of O-acetylation.•O-antigen gene clusters are essentially identical between the two strains.

The O-polysaccharides (O-antigens) were isolated by mild acid degradation of the lipopolysaccharide (LPS) of Escherichia coli O46 and O134. The structures of their linear tetrasaccharide repeating units were established by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy: .where d-aThr indicates d-allothreonine and R indicates O-acetyl substitution (∼70% on aThr and∼15% on GalNAc) in E. coli O46 whereas the O-acetylation is absent in E. coli O134. Functions of genes in the essentially identical O-antigen gene clusters of E. coli O46 and O134 were tentatively assigned by a comparison with sequences in available databases and found to be in agreement with the O-polysaccharide structures established.

Graphical abstractd-aThr indicates d-allothreonine. Non-stoichiometric O-acetylation occurs only in Escherichia coli O46.Figure optionsDownload full-size imageDownload as PowerPoint slide