Transfection of Vibrio cholerae by bacteriophage phi 149 DNA

DNA isolated from Choleraphage ø149 of Group IV was infectious when mixed with competent $\text{V.}\text{cholerae}$ cells. The cells were competent during mid-log phase of growth. The infectivity of phage DNA was destroyed by deoxyribonuclease but not by ribonuclease or pronase. About 5 min is required for the establishment of the DNase resistant state. The dose response curve for transfection suggested that 2 to 3 molecules of DNA are required to produce one infections center. An infectivity of 5 × 10⁴ infectious center per μg of DNA was obtained.