Temperature-sensitive mutants of B. subtilis defective in deoxyribonucleotide synthesis

Summary Cessation of DNA synthesis in the temperature sensitive mutant 167 tsA 13 of Bacillus subtilis is correlated with the disappearance of dCTP and dATP pools at the nonpermissive temperature; dGTP and dTTP residual pools are stable. In the presence of AdR and CdR at 45°C, the dCTP and dATP pools remain normal and the cells continue to synthesise DNA and grow. It is inferred that in 167 tsA 13 AdR and CdR kinases exist, that the deoxynucleotide kinases function normally and the ribonucleotide reduction is deficient. B. subtilis strains have a hydroxyurea sensitive reductase and the drug inhibition can be reversed by exogenous deoxynucleosides. Evidence that the tsA 13 mutation is in the structural gene of the ribonucleotide reductase is discussed.