GENETIC TRANSFORMATION IN ESCHERICHIA COLI

The earlier observation of a DNA-induced genetic change in the cells of an auxotrophic strain Escherichia coli 113-3 dependent on vitamin B12 or methionine for growth has been confirmed and extended, and a method for the isolation of biologically active DNA is described. Optimum conditions for transformation have been determined with respect to the pH of the cell lysate during extraction, concentration of DNA in the system and the temperature at which the competent cells are exposed to DNA. It is shown that the competence of the cells reaches a peak at the middle of the logarithmic phase of growth. A comparison of vitamin B12 content and methionine-synthesizing abilities of the donor, recipient and transformed strains has confirmed the rehabilitation of the mutants to prototrophy. This observation has been extended to other strains of E. coli as donors and acceptors. © 1969.