Extracellular polysaccharides and agglutination to soft rot bacteria

ABSTRACT

Erwinia caratovora subsp. carotovora and subsp. atroseptica produced viscous substances in 5% sucrose culture medium. The chemical analysis of alcohol-insoluble precipitate was positive for carbohydrate, negative for protein and consist of xylose and galactose and sometimes of galactose only. The subspecies carotovora produced free-EPS two-three-fold more than the subsp. atroseptica. Exopolysaccharides of the subsp. carotovora was found to cause reversible wilting of tomato cuttings. Moreover, the unwashed cells induced soft rot for potato and pepper fruits two-five fold more than the washed ones, indicating the important role of EPS in pathogenesis. The highest concentration [600 micro, g/ml]of the three buffered fractions [A,B and C] prepared from corn grains strongly agglutinated the bacterial cells of E.carotovora subsp. carotovora and subsp. atroseptica. At the lower concentrations [150 micro.g/ml] of fractions A and C, the washed cells of both subsp. were agglutinated, whereas the unwashed were not. These results indicate the necessity of EPS for full virulence of subsp. carotovora