Structure Elucidation of Escherichia Coli Serogroup O188 O Antigen

PS2 Poster session 2 Even numbers
Location (hall): 
Start/end time: 
Tuesday, July 2, 2019 - 15:45 to 17:15

Axel Furevi1, Jonas Ståhle1, Claudio Muheim2, Spyridon Gkotzis3, Daniel O. Daley2, Klas Udekwu3, Göran Widmalm1

1Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm, Sweden, 2Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden, 3Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden

The lipopolysaccharide (LPS) is located on the outer surface of gram-negative bacteria and builds up a protective barrier against its environment and potential threats. The O antigen polysaccharide part of the LPS is the main tool for determining the serotype of different strains. So far, the E. coli strains are distributed in 180 serogroups with only a few left to elucidate. Here, we present the structure of the E. coli O188 polysaccharide. The O antigen polysaccharide was obtained utilizing hot phenol-water extraction, mild acid delipidation and purified with size exclusion chromatography. Sugar analysis and absolute configuration analysis using chemical derivatization and gas liquid chromatography showed the sugar units: D-Gal, D-GlcNAc, D-GlcA and D-Man and a combination of 1D and 2D ¹H,¹³C NMR spectroscopy experiments revealed a pentasaccharide repeating unit. The structure of the repeating unit, which was predicted using the computer program CASPER and confirmed by NMR spectroscopy, is the branched pentasaccharide: