Aphidicolin-resistant mutants of bacteriophage φ29: Genetic evidence for altered DNA polymerase

Abstract Aphidicolin-resistant mutants (Aph r ) of Bacillus subtilis bacteriophage φ29 were isolated after mutagenesis with hydroxylamine. Efficiency of plating (e.o.p.) of the resistant mutants was not reduced at 500 μ M aphidicolin, although e.o.p. of wild type φ29 was less than 10 −5 at the same concentration of aphidicolin. By recombination and complementation analyses, both sites of the mutations, aph -71 and aph -101, of Aph r 71 and Aph r 101, respectively, were mapped in gene 2 which encodes φ29 DNA polymerase. The activity of wild type φ29 DNA polymerase, in a partially purified fraction, was inhibited by aphidicolin. DNA polymerases from Aph r 71 and Aph r 101, prepared in the same manner as that of wild type, were resistant to the drug. These results indicate that the acquisition of the aphidicolin resistance of Aph r 71 and Aph r 101, of bacteriophage φ29 results from a structural alteration of φ29 DNA polymerase which reduces sensitivity to aphidicolin.