FIG 4.

Sensitivity of M. smegmatis ohr-ohrR mutants to peroxides. MSWt, an M. smegmatis wild-type strain; MSΔohr, an M. smegmatis ohr mutant strain; MSΔohr/c, an M. smegmatis ohr mutant complemented with functional ohr using plasmid pMVMSOHRR; MSΔohrR, an M. smegmatis ohrR mutant strain; MSΔohrR/c, an M. smegmatis ohrR mutant complemented with functional ohrR using plasmid pMVMSOHRR; MSΔohr-ohrR, an M. smegmatis ohr-ohrR mutant strain; MSΔohr-ohrR/c, an M. smegmatis ohr-ohrR mutant complemented with functional ohr-ohrR using plasmid pMVMSOHRR; MS206, an M. smegmatis wild-type strain bearing plasmid pMV206; MSohrE, an M. smegmatis wild type bearing plasmid pMVMSOHR2. (A) Growth-inhibitory effects of peroxides in a disk inhibition assay. Each disk received 10 μl of either 250 mM H₂O₂, 250 mM t-BHP, or 150 mM CHP. The bars show the diameters of the zones of inhibition. P values are shown for the groups compared. Values are significantly lower/higher than the values obtained for strain MSWt. (B) Disk inhibition on plates. Agar plates showing growth inhibition by CHP are shown for a few representative strains.