Figure 2.

In the absence of gyrase, inhibition of topo IV causes rapid replication arrest. (A) E. coli strains acrA parE⁺ (□) and acrA parE^ts (○) were grown at 30°C. At time 0, novobiocin (Nov) was added to 5 μg/ml, and the cultures were simultaneously shifted to 42°C. The rates of DNA synthesis were measured at the indicated times. (B) S. typhimurium strains gyrA208 (gyrA^ts, ▪) and gyrA208parE^ts (●) were grown at 30°C. At time 0, they were shifted to 44°C. The rates of DNA synthesis were measured at the indicated times after temperature shift.