FIG 3 .

Importance of prxA in response to NO and H₂O₂ under microaerobic conditions. The growth of a strain of V. cholerae lacking prxA and its adjacent gene vc2638 was compared to that of the wild type (WT) and a ΔhmpA mutant in the absence (A) or presence (B) of 10 µM DETA-NONOate under microaerobic conditions in minimal medium. In the experiment shown in panel C, wild-type and ΔnorR mutant strains of V. cholerae containing a reporter plasmid that contains lacZ fused to the prxA promoter were grown in minimal medium. After the addition of 50 µM DEA-NONOate (gray bars), 100 µM H₂O₂ (black bars), or nothing (white bars), prxA promoter activity was measured by Miller assay.