Structural and genetic characterization of the O-antigen of Escherichia coli O161 containing a derivative of a higher acidic diamino sugar, legionaminic acid

The O-antigen is an essential component of lipopolysaccharide on the surface of Gram-negative bacteria and plays an important role in its pathogenicity. Composition and structure of the O-antigens of Escherichia coli are highly diverse mainly due to genetic variations in the O-antigen gene cluster. In this work, the chemical structure and the gene cluster of the O-antigen of E. coli 0161 were studied. Chemical degradations, sugar analyses, and NMR spectroscopy showed that the 0161 antigen possesses a trisaccharide O-repeating unit containing a 5-N-acetyl-7-N-(D-alanyl) derivative of 5,7-diamino-3,5,7,9-tetradeoxy-oglycero-D-galacto-non-2-ulosonic (legionaminic) acid (Leg5Ac7Ala) and having the following structure: -> 8)-alpha-Legp5Ac7Ala-(2 -> 4)-beta-d-GlcpA-(1 -> 3)-beta-d-GlcpNAc-(1 -> The O-antigen gene cluster of E. coli O161 was sequenced. In addition to the genes encoding sugar transferases, O-repeating unit flippase (Wzx) and O-antigen polymerase (Wzy), the genes involved in the biosynthesis of a legionaminic acid derivative were identified based on database similarities. (C) 2010 Elsevier Ltd. All rights reserved.