Fate of transforming DNA after uptake by competent Bacillus subtilis: failure of donor DNA to replicate in a recombination-deficient recipient.

The fate of radioactively-labeled transforming DNA was studied in a recombination-deficient strain of Bacillus subtilis that carried the recB2 mutation (Rec(-)) and was sensitive to radiation. Experiments performed with extracts of this strain after transformation showed that the recovery of donor transforming activity and the appearance of recombinant transforming activity occurred to the same extent as in the Rec(+) strain. Sucrose gradient analyses revealed that donor-recipient complex is also formed to the same extent in the Rec(-) and Rec(+) strains, but that 80-90% of the donor genetic material in the complex failed to replicate in the Rec(-) mutant.