FIG. 3.

Effect of As(III) on transcription of arsR and arsB in wild-type bacteria and crc, gor, and sodA sodB mutants. Bacteria were grown to mid-logarithmic phase and exposed to 1 mM As(III) for 2 h at 37°C, and cell extracts were prepared and assayed for β-galactosidase activity in triplicate as described in Materials and Methods. White bars, arsR-lacZ; black bars, arsB-lacZ. Lanes 1 and 5, wild type; lanes 2 and 6, crc mutant; lanes 3 and 7, gor mutant; lanes 4 and 8, sodA sodB mutant. Lane 9 represents the lacZ plasmid control.