Structures of the O-specific polysaccharides from Yokenella regensburgei (Koserella trabulsii) strains PCM 2476, 2477, 2478, and 2494: High-resolution magic-angle spinning NMR investigation of the O-specific polysaccharides in native lipopolysaccharides and directly on the surface of living bacteria

The structures of the carbohydrate O-specific side-chain moiety of the lipo polysaccharides (LPS) of Yokenella regensburgei, strains PCM 2476, 2477, 24 78, and 2494, have been investigated by H-1 and C-13 NMR, fast atom bombard ment tandem mass spectrometry (FAB-MSMS), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, methylation analys is, partial acid hydrolysis, and immunological methods. It was concluded th at the O-specific polysaccharides of strains 2476, 2477, 2478, and 2494 are composed of the same basic trisaccharide repeating unit having the structu re -->3)-alpha-D-FucpNAc-(1-->2)-L-alpha-D-Hepp-(1-->3)-6-deoxy-alpha-L-Tal p-(1-->, in which L-alpha-D-Hepp is L-glycero-alpha-D-manno-heptopyranose. The detailed analysis revealed, however, differences in O-acetylation patte rns of the 6-deoxy-L-talose residue, with 2- and 4-O-acetyl disubstituted - ->3)-6-deoxy-alpha-L-Talp-(1--> in strain PCM 2476 and a 2-O-acetylated res idue in strains 2477, 2478, and 2494. These structures represent novel, tri saccharide repeating units of bacterial O-antigens that are characteristic and unique to the Y. regensburgei species. By use of the high-resolution ma gic-angle spinning (HR-MAS) technique, H-1 NMR spectra of the O-polysacchar ides directly in isolated LPS were obtained. This allowed for almost full a ssignment and structural determination of the polysaccharide. By this techn ique the O-polysaccharide components were also observed in their original f orm directly on the surface of living bacterial cells.