Structure of the O-polysaccharide of Providencia alcalifaciens O3 containing 3,6-dideoxy-3-formamido-D-glucose and D-galacturonamide.

Mild acid degradation of the lipopolysaccharide (LPS) of Providencia alcalifaciens O3 followed by GPC on Sephadex G-50 and anion-exchange chromatography on DEAE-Trisacryl M afforded neutral and acidic polysaccharides, LPS core oligosaccharide, and an oligosaccharide composed of one repeat of the neutral polysaccharide (O-unit) linked to the LPS core. The following structure of the pentasaccharide O-unit was established by sugar and methylation analyses, 2D (1)H and (13)C NMR spectroscopy and ESI MS: [formula: see text] where Qui3NFo stands for 3,6-dideoxy-3-formamidoglucose and GalAN for galacturonamide. The LPS core is represented by the Glc(3)Gal(1)GalA(1)Hep(3)Kdo(1)Ara4N(1)P(3)EtN(2) glycoform reported earlier for P. alcalifaciens O9, O34, and O19. The acidic polysaccharide had the same peptidoglycan-like structure as a polysaccharide isolated earlier from P. alcalifaciens O24, O38, and O45, and, most likely, represents bacterial capsule material.