Fig 7.

Rifampin-resistant mutants are still sensitive to interference with the CarD/RNAP interaction. (A) Survival of M. smegmatis strains during rifampin treatment. The M. smegmatis strains resistant to rifampin due to substitutions in RNAP β at either position S438 (β^S438F) or H442 (β^H442R) were engineered to express either CarD^WT or CarD^R25E. The log-phase β^S438F CarD^WT, β^S438F CarD^R25E, β^H442R CarD^WT, and β^H442R CarD^R25E cultures in LB were treated for 1 h with 500 μg/ml in rifampin. After treatment, dilutions were plated on LB, and survival was determined as a ratio of CFU after treatment to that in untreated cultures. The graph shows the mean ± SEM, and each sample is represented by a black circle. (B and C) Representative growth curves from 4 replicates each of M. smegmatis β^S438F CarD^WT (open circles), β^S438F CarD^R25E (open squares), β^H442R CarD^WT (closed circles), and β^H442R CarD^R25E (closed squares) in LB. (D) Survival of M. smegmatis strains during H₂O₂ treatment. The log-phase M. smegmatis β^S438F CarD^WT, β^S438F CarD^R25E, β^H442R CarD^WT, and β^H442R CarD^R25E cultures were treated for 1 h with 25 mM H₂O₂. After treatment, dilutions were plated on LB, and survival was determined as a ratio of CFU after treatment to that in untreated cultures. The graph shows the mean ± SEM, and each sample is represented by a black circle. The significance levels were determined as described for Fig. 3.