Structural Determination and Genetic Identification of the O-Antigen from an Escherichia coli Strain, LL004, Representing a Novel Serogroup

Abstract

The O-antigen is the outermost component of the lipopolysaccharide layer in Gram-negative bacteria, and the variation of O-antigen structure provides the basis for bacterial serological diversity. Here, we determined the O-antigen structure of an Escherichia coli strain, LL004, which is totally different from all of the E. coli serogroups. The tetrasaccharide repeating unit was determined as →4)-β-d-Galp-(1→3)-β-d-GlcpNAc6OAc(~70%)-(1→3)-β-d-GalpA-(1→3)-β-d-GalpNAc-(1→ with monosaccharide analysis and NMR spectra. We also characterized the O-antigen gene cluster of LL004, and sequence analysis showed that it correlated well with the O-antigen structure. Deletion and complementation testing further confirmed its role in O-antigen biosynthesis, and indicated that the O-antigen of LL004 is assembled via the Wzx/Wzy dependent pathway. Our findings, in combination, suggest that LL004 should represent a novel serogroup of E. coli.

Structural and Genetic Identification of the O-Antigen from an Escherichia coli Isolate, SD2019180, Representing a Novel Serogroup

“…In addition, many putative additional serogroups were characterized by analyzing their O-AGCs, but structural data supporting their identity are missing [14][15][16]. In our previous work, an E. coli strain, LL004, representing a novel serogroup, was identified by using combined structural and genetic analysis [17]. Here, we established the O-antigen structure of another enteropathogenic E. coli strain, SD2019180, which has not been reported previously.…”