New fructan — the O-specific polysaccharide from Escherichia coli O92

The structure of the O-specific polysaccharide (O-antigen) from Escherichia coli O92 was established. The acid-labile polysaccharide was produced by O-deacylation of the lipopolysaccharide under mild alkaline conditions. The methylation analysis combined with 1D and 2D ¹H and ¹³C NMR spectroscopy demonstrated that the O-specific polysaccharide chain of the lipopolysaccharide is a linear fructan composed of mono-О-acetylated disaccharide repeating units having the structure →1)-β-D-Fruf3Ac-(2→3)-β-D-Fruf-(2→. To the best of our knowledge, this fructan has been hitherto unknown in bacteria.