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

Abstract

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 1H and 13C NMR spectroscopy and ESI MS: →3)-α-d-GalpAN-(1→4)-α-d-GalpNAc-(1→4)-α-d-Galp-(1→3)-β-d-GalpNAc-(1→α-d-Quip3NFo-(1→4) where Qui3NFo stands for 3,6-dideoxy-3-formamidoglucose and GalAN for galacturonamide. The LPS core is represented by the Glc3Gal1GalA1Hep3Kdo1Ara4N1P3EtN2 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.