Extracellular polysaccharide of Erwinia chrysanthemi CU643

Erwinia chrysanthemi are gram-negative bacterial phytopathogens causing soft rots in a number of plants. The structure of the extracellular polysaccharide (EPS) produced by E. chrysanthemi strain CU643, pathogenic to Philodendron, has been determined using a combination of chemical and physical techniques including methylation analysis, high- and low-pressure gel-filtration and anion-exchange chromatography, high-pH anion-exchange chromatography, partial acid hydrolysis, mass spectrometry, and 1- and 2-D NMR spectroscopy. In contrast to the structures of the EPS reported for other strains of E. chrysanthemi, the EPS from strain CU643 is a linear polysaccharide containing l-Rhap, d-Galp, and d-GlcAp in the ratio 4:1:1. Evidence is presented for the following hexasaccharide repeat unit:→3)-β-d-Galp-(1→2)-α-l-Rhap-(1→4)-β-d-GlcAp-(1→2)-α-l-Rhap-(1→2)-α-l-Rhap-(1→2)-α-l-Rhap-(1→ (1)