[Characteristics of Salmonella mutants competent for isolated nucleic acids]

The method for the isolation of transfectable salmonellae by growing them in a liquid medium for a long time and selecting R-clones, subsequently tested in the Ca2+-dependent transfection of the DNA of bacteriophage P22 H5, was developed. The probability of obtaining transfectable clones varied between 18.3% and 48.3% in different Salmonella strains. Testing their sensitivity to specific bacteriophages used for the determination of structural distortions in the lipopolysaccharide layer of the cell wall made it possible to divide transfectable Salmonella clones into 3 phenotypical groups. The effectiveness of the formation of transfectants in the Ca2+-dependent transfection of the DNA of bacteriophage P22 H5 increased to 4.0 X 10(-8) - 8.0 X 10(-8) in the isolated R-clones of S. typhimurium strain SU453. In contrast to the initial strain, these R-clones were characterized not only by more effective transfection, but also by the possibility of plasmid transformation.