Abstract
Phenol-extracted DNA from mycoplasma virus L2 was able to transfect Acholeplasma laidlawii in the presence of polyethylene glycol. Transfection was sensitive to DNase and was most efficient with 36% (wt/vol) polyethylene glycol 8000 and cells in logarithmic growth. Virus production by the transfected cells was similar to that of the cells infected by intact virus. L2 DNA transfected A. laidlawii with a single-hit dose-response curve, reaching saturation at high DNA concentrations. Optimum transfection frequencies were about 10(-7) transfectants per L2 DNA molecule and 10(-4) transfectants per CFU. When DNA was present in saturating amounts, the number of transfectants increased linearly with the number of CFU present in the transfection mixture, suggesting that DNA uptake does not occur by a mechanism involving cell fusion. The cleavage of the superhelical mycoplasma virus L2 genome with restriction endonucleases that cleave the DNA molecule once reduced the transfection frequency. Host cell modification and restriction of transfecting L2 DNA were similar to those for infecting L2 virions.