FIG 4.
A rho-null mutation or bicyclomycin reduces β-lactam susceptibility. (A) Schematic representation of the location of the rhoG56C substitution. The conserved motifs were identified using the NCBI Conserved Domain database (http://www.ncbi.nlm.nih.gov/Structure/cdd/wrpsb.cgi). (B) Effect of the rho gene deletion on the sensitivity of B. subtilis to CEF. MICs were determined using an Etest assay. (C) Effect of bicyclomycin inhibition on the sensitivity of B. subtilis to CEF. Treatment with the Rho inhibitor bicyclomycin increases the CEF MIC in a concentration-dependent manner. MICs were determined by the growth inhibition assay in MH broth. The data are reported as median values from three independent experiments. The MIC endpoint was established after 16 h of incubation. (D) Effect of the rho gene deletion on the sensitivity of B. subtilis to broad-spectrum β-lactams. Disk diffusion assays were performed on MH agar plates. Three independent experiments were performed for each strain, and the standard deviations are indicated by error bars. (E) Effect of the penP gene deletion on CEF resistance in the rho-null mutant. A representative data set from the disk diffusion assay is shown.