Ethidium bromide susceptibility in the MtΔP27 mutant. Bacterial strains grown to mid-log phase were diluted in 7H9 medium either with (blue and gray lines) or without (black lines) 1 μg/ml (full lines) or 0.5 μg/ml (dotted lines) of ethidium bromide and growth was determined over time as indicated. Assays were performed in the presence (blue lines) or absence (black and gray lines) of 20 μg/ml reserpine. Growth curves of a: H37Rv, b: MtΔP27 c: MtΔP27::P27, d: MtΔP27:: P55 and e: MtΔP27::P27-P55 are representative of two independent experiments. *Significantly different from values of H37Rv (p < 0.05).