Extracellular polysaccharide of Erwinia chrysanthemi CU643

Abstract

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-Rha p, d-Gal p, and d-GlcA p 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)