Extracellular polysaccharide of Erwinia chrysanthemi CU643

Erwinia chrysanthemi are gram-negative bacterial phytopathogens causing sof t rots in a number of plants. The structure of the extracellular polysaccha ride (EPS) produced by E. chrysanthemi strain CU643, pathogenic to Philoden dron, has been determined using a combination of chemical and physical tech niques including methylation analysis, high- and low-pressure gel-filtratio n and anion-exchange chromatography, high-pH anion-exchange chromatography, partial acid hydrolysis, mass spectrometry, and 1- and 2-D NMR spectroscop y. In contrast to the structures of the EPS reported for other strains of E . chrysanthemi, the EPS from strain CU643 is a linear polysaccharide contai ning L-Rhap, D-Galp, and D-GlcAp in the ratio 4:1:1. Evidence is presented for the following hexasaccharide repeat unit: --> 3)-beta-D-Galp-(1 --> 2)-alpha-L-Rhap-(1 --> 4)-beta-D-GlcAp-(1 --> 2)- alpha-L-Rhap -(1 --> 2)-alpha-L-Rhap-(1 --> 2)-alpha-L-Rhap-(1 --> (1) (C) 1999 Elsevier Science Ltd. All rights reserved.