DNA gyrase inhibitors block development of Bacillus subtilis bacteriophage SP01

SP01 development was inhibited by nalidixic acid and novobiocin in the sensitive host Bacillus subtilis 168M. Inhibition by novobiocin was prevented by a Novr mutation in the cellular DNA gyrase gene. Nalidixic acid inhibition persisted in hosts carrying a Nalr gyrase, but could be overcome by phage mutation. We conclude that SP01 requires for its development subunit B of the host DNA gyrase, but replaces or modifies subunit A.