[DNA compact form in solution. VII. Transforming activity of precompact forms of DNA]

Data on transforming activity of DNA in water-salt (0.3 M NaCl) solutions containing polyethylene glycol (PEG) are presented. Bacillus subtilis deficient mutant lys 42 and prototrophic strain SHgw were used as recipient and donor, respectively, for transformation experiments. It has been shown that when PEG concentrations were increased the relative experiments. It has been shown that when PEG concentrations were increased the relative transforming activity (RTA) at first (at PEG concentrations approximately 30-40 mg/ml) increased to the value of 200-250%, then began to decrease. At PEG concentrations approximately 100-125 mg/ml, when DNA molecules form compact particles, the RTA does not exceed 10%. The observed changes in RTA are interpreted as a result of conformational changes of double-stranded DNA molecules. The increase in the RTA at low PEG concentrations may be explained as an increase in transforming activity of the precompact form of DNA, while the decrease in RTA at PEG concentrations exceeding 60-70 mg/ml was believed to be connected with the fact that compact particles of DNA could not penetrate through the walls of bacterial cells.