Evaluating ArcA binding site 1 (ABS-1) functionality at the ompW promoter. (A) Schematic representation of substitutions generated at the ompW promoter. Substituted bases are in red, underlined and shown below the core ArcA binding sequence. Black box indicates ABS-1. -35 is indicated. (B) Expression of the wild type and mutagenized regulatory region of ompW in S. Typhimurium. Strain 14028s was transformed with the reporter plasmids pompW-lacZ (wild type) or pompW/ABS1-lacZ (ABS-1 mutated). Cells were grown to OD ~ 0.4 and treated with H2O2 1.5 mM or NaOCl 530 μM for 20 min and β-galactosidase activity was measured. Values represent the average of three independent experiments ± SD.