Structural Elucidation and genetic identification of the O-antigen from a novel serogroup of Escherichia coli strain 2017LL031

Abstract

The O-antigen is an important virulence factor involved in the survival, virulence and invasion of bacteria. The bacterial serological types are highly dependent on these surface-exposed and structurally unique O-antigen structures. In this work, the structure of O-antigen from an Escherichia coli strain 2017LL031 was elucidated as a hexasaccharide repeating unit: →3)-[β-D-Glcp-(1 → 2)]-α-L-Rhap-(1 → 3)-[α-D-Quip-(1 → 3)-α-D-GlcpA-(1 → 2)]-β-L-Fucp-(1 → 3)-β-D-GlcpNAc-(1→, which is completely different from all known E. coli serogroups. The O-antigen gene cluster (O-AGC) of 2017LL031 was also analyzed and correlates well to its O–Ag. Moreover, the O-AGC of 2017LL031 was deleted and its role in O–Ag biosynthesis was confirmed experimentally. Taken together, our results present that a novel E.coli serotype 2017LL031 is identified.