FIGURE 4.

SecA2 K129R is dosage-dependent. Wild type and ΔsecA2 mutant M. smegmatis strains were transformed with pNR54 encoding inducible secA2 K129R under control of the Tet ON promoter. Strains were grown in Mueller Hinton broth with different concentrations of Atc (closed circle, 0 ng/ml; open circle, 100 ng/ml; closed triangle, 200 ng/ml). Growth of wild type (A) and ΔsecA2 mutant (B) was monitored by measuring A_{600 nm}. At 21 h post-inoculation, serial dilutions of the wild type (C) and ΔsecA2 mutant (D) from each culture in the growth curve were plated onto Mueller Hinton plates, all of which contained 500 ng/ml Atc. Shown are colonies on plates incubated at 37 °C for 3–4 days. Even after extended incubation, colonies did not appear from cultures treated with 200 ng/ml Atc during liquid growth.