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 lipopolysaccharides (LPS) of Yokenella regensburgei, strains PCM 2476, 2477, 2478, and 2494, have been investigated by (1)H and (13)C NMR, fast atom bombardment tandem mass spectrometry (FAB-MSMS), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, methylation analysis, partial acid hydrolysis, and immunological methods. It was concluded that the O-specific polysaccharides of strains 2476, 2477, 2478, and 2494 are composed of the same basic trisaccharide repeating unit having the structure -->3)-alpha-D-FucpNAc-(1-->2)-L-alpha-D-Hepp-(1-->3)-6-deoxy -alpha-L- Talp-(1-->, in which L-alpha-D-Hepp is L-glycero-alpha-D-manno-heptopyranose. The detailed analysis revealed, however, differences in O-acetylation patterns 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 residue in strains 2477, 2478, and 2494. These structures represent novel, trisaccharide repeating units of bacterial O-antigens that are characteristic and unique to the Y. regensburgeispecies. By use of the high-resolution magic-angle spinning (HR-MAS) technique, (1)H NMR spectra of the O-polysaccharides directly in isolated LPS were obtained. This allowed for almost full assignment and structural determination of the polysaccharide. By this technique the O-polysaccharide components were also observed in their original form directly on the surface of living bacterial cells.