PROTEINS UNIQUE TO PHENOTYPICALLY DISTINCT GROUPS OF XANTHOMONAS-CAMPESTRIS PV VESICATORIA REVEALED BY SILVER STAINING

Silver staining of sodium dodecyl sulfate-lysed cells of Xanthomonas c ampestris pv. vesicatoria electrophoretically separated in polyacrylam ide gel revealed broad, dark gray bands in the low molecular weight re gion. The molecular weight of these bands was characteristic for each of the two major phenotypic groups identified in our X. c. vesicatoria collection. A 32- to 35-kDa band, designated alpha, was present in 19 2 of 197 tomato race 1 strains; whereas, a 25- to 27-kDa band, designa ted beta, was present in all 55 strains of tomato race 2. Race 1 strai ns expressing an alpha band were unable to hydrolyze starch (Amy(-)), and very few degraded pectate (Pec(-)). In contrast, most race 2 strai ns were Amy(+) and Pec(+). The alpha and beta bands, which are unique to each of the X. c. vesicatoria subpopulations, were not revealed whe n the Coomassie blue or copper staining protocols were used and were c haracterized as heat-stable proteins. Silver staining of protein profi les and testing for amylolytic activity of the bacterium are relativel y simple tests that can help assign uncharacterized strains to each X. c. vesicatoria phenotypic group.