[Entobacterial transformation by R6K plasmid DNA].

Preparations of DNA of R6K plasmide obtained by various methods on the basis of the "clarified" lysate: by gel filtration on sepharose 4B, centrifugation in cesium chloride with ethidium bromide gradient, were analysed in the E. coli C600. S. typhimurium AG37, Pr. vulgaris 4636, S. marcescens 20-10 transformation. The frequency of transformation proved to depend on the extent of DNA purification. Factors influencing the E. coli C600 competence and the transformation efficacy (the phase of the culture growth, the concentration of cells in the mixture with DNA, theCaCl2 concentration, the time of the cell incubation at 42 degrees C) were studied. Kinetics of the phenotypical expression of the plasmide signs of ampicillin and streptomycin resistance in transformation was also studied in this work.