[Use of gen5 and gen6 ts-mutants of phage T3 as indicators of inhibitors of DNA synthesis].

In an enzyme-specific drug screening system nalidixic acid and 3'-FTdR, inhibitors of DNA synthesis, both reduce the growth of wild type and temperature-sensitive point mutants of phage T3 with different efficiencies. The wild type shows the strongest sensitivity against the drugs, while an exonuclease mutant is the most insensitive variant. The DNA polymerase mutants exhibit an intermediate degree of inhibition. The anthracycline antibiotics violamycin BI and adriblastin which preferentially inhibit RNA synthesis show the same degree of inhibition for all mutants. This is true also for the RNA synthesis inhibitor lambdamycin, which is identical with chartreusin. The protein synthesis inhibitors chloramphenicol and o-phenanthroline, a chelating agent, impair all mutants to the same extent. Our data confirm the hypothesis that structural variants of essential viral enzymes, when compared with the wild type should reveal different sensitivities against specific inhibitors and show that this T3 system could be used for the indication of specific inhibitors of DNA synthesis.