Structure of an abequose-containing O-polysaccharide from Citrobacter freundii O22 strain PCM 1555

The lipopolysaccharide of Citrobacter freundii O22 (strain PCM 1555) was degraded under mild acidic conditions and the O-polysaccharide released was isolated by gel chromatography. Sugar and methylation analyses along with H-1 and C-13 NMR spectroscopy, including two-dimensional H-1,H-1 ROESY and H-1,C-13 HMBC experiments, showed that the repeating unit of the O-polysaccharide has the following structure: [GRAPHICS] where Abe is abequose (3,6-dideoxy-D-xylo-hexose). SDS-PAGE and immunoblotting revealed that the O-antigen of C. freundii O22 is serologically indistinguishable from those of Salmonella group B serovars (Typhimurium, Brandenburg, Sandiego, Paratyphi B) but not related to other abequose-containing O-antigens tested (Citrobacter werkmanii O38 and Salmonella Kentucky) or colitose (L enantiomer of abequose)containing O-antigen of Escherichia coli O111. (C) 2009 Elsevier Ltd. All rights reserved.