FIG 5.

Sensitivity of M. smegmatis strains to INH. All strains except MSΔahpC are described in the legend to Fig. 4. MSΔahpC is an M. smegmatis ahpC mutant strain. (A) Disk inhibition assay. Each disk received 10 μl of INH (1 mg/ml). P values are shown for the groups compared, and the values are significantly lower/higher than the values obtained for strains MSWt and MSΔohrR/c. (B) Disk inhibition on plates. Agar plates showing growth inhibition by INH are shown for a few representative strains. (C) MICs of INH. The MICs of INH were determined by the tube dilution method, and the lowest dilution of isoniazid inhibiting the growth of the M. smegmatis strains was considered the MIC. (D) Catalase activity with whole-cell lysates. Each reaction mixture contained 1 mM the substrate H₂O₂ and 0.2 mg of the total cell lysate protein. The reactions were stopped after 1 min by addition of 50 μl of a catalase quencher, and the absorbance was read at 520 nm.