FIG. 4.
Overproduction of AhpC, AhpD, and OxyR and their contribution to resistance against oxidants. (A) Overproduction of AhpC and AhpD proteins. S. lividans cells containing oxyR (pJHOxyR), ahpCD (pJHAhpCD), or ahpC (pJHAhpC) genes on multicopy plasmid pIJ702 were grown on NA plates containing thiostrepton (50 μg/ml) until they formed substrate mycelium (24 h) or aerial mycelium (36 h). The amount of CatA, CatC, AhpC, and AhpD proteins in cell extracts was determined by Western blot analysis. (B) Effect of overproduction on resistance against hydrogen peroxide and cumene hydroperoxide. About 106 spores of cells harboring plasmids were transferred to plates of NA medium containing 200 μM hydrogen peroxide, 150 to 200 μM cumene hydroperoxide (CHP), or no oxidants (control) with thiostrepton (50 μg/ml). Cells were incubated at 30°C for 3 days.