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Isolation and Characterization of Extracellular Polysaccharide of Clavibacter michiganensis subsp. sepedonicus. A. A. G. Westra, Research support specialist and Uihlein professor of plant pathology, Department of Plant Pathology, Cornell University, Ithaca, NY 14853; S. A. Slack, Research supported by Wisconsin State Potato Board and College of Agricultural and Life Sciences, University of Wisconsin-Madison (Project B459). Phytopathology 82:1193-1199. Accepted for publication 29 June 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-1193.

The extracellular polysaccharide (EPS) of Clavibacter michiganensis subsp. sepedonicus, the causal organism of bacterial ring rot of potato, consists of four components (IIV) that were separated on the basis of size and charge. These components were homogenous according to ion-exchange and/or gel permeation chromatography, to analysis of neutral sugar composition, and by reaction with polyclonal antisera. All components contained fucose, mannose, galactose, and glucose, although the ratios of these monosaccharides varied with strain and the culture medium in which the strains were grown. Components I and II appeared to be aggregates of component III, whereas component IV was of distinct composition. Protein associated with components I and III was not covalently bound and could be separated from the polysaccharides by DEAE-cellulose chromatography with an NaCl gradient. Spent culture fluid containing these EPS components induced wilting in potato cuttings. Nonfluidal colony morphology was correlated with lack of production of EPS components I and III for two strains but was not correlated with avirulence or attenuation of bacterial ring rot symptoms in eggplant or potato.