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Transformation studies on Pseudomonas solanacearum. Phelps, Ralph Howard


The process of transformation has been demonstrated in Pseudomonas solanacearum. The DNA isolated from various virulent strains of the pathogen induced formation of wild-type virulent cells in pure cultures of weakly virulent strains of the organism. DNase completely inhibited the reaction. Cultures of transformed cells were found to be equally as pathogenic to tomato as the wild, virulent strains. The cells of both cultures were also shown to possess similar capacities for storing poly β-hydroxy butyric acid. Various comparative studies were carried out on virulent and weakly virulent strains of one of the isolates used in the transformation experiments. DMAs isolated from cells of the two strains were found to have identical G-C values, as determined by their buoyant densities in CsCl and their thermal denaturation temperatures. The organisms also manifested similar reactions in several biochemical tests commonly used in the identification of bacterial species. Antisera were prepared against the cells and extracellular products of both strains. Serological studies indicated the presence of common antigenic determinants among the four different antigens. However, evidence was produced which suggested some heterogeneity of antigenic components. Chromatographic analyses of the extracellular products of the two strains indicated no qualitative differences in the sugar or amino acid components. Glucose, fructose, galactosamine and mannose were the sugars detected, while the amino acid components included leucine, phenylalanine, methionine, lysine, glycine, glutamic acid, alanine, hydroxyproline and an unidentified amino acid. The latter moved at the same rate as histidine but gave a different colour with ninhydrin spray. An argument attempting to coordinate results of the two phases of the study was presented. Further, the significance of the phenomenon of transformation in the biology of Pseudomonas solanacearum was briefly discussed.

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