Fig 1. Activators and inhibitors of the SOS Response in E. coli.

Panels A and B, induction and inhibition of recA in STEC strains by qRT-PCR. Panel A, effect of mitomycin C on recA expression in STEC EDL933. Panel B, effects of ciprofloxacin and zinc acetate on recA expression in STEC TSA14. Panels C-H, effects of inducers and inhibitors of recA as measured using the Miller Assay and reporter strain JLM281. For all panels the activators and inhibitors were added 1 h after beginning the subculture in DMEM broth. *, significant by ANOVA compared to ciprofloxacin alone. In panels E-F the inhibitory effect of zinc on zidovudine-induced recA was significant for 0.2 mM and higher, despite the lack of asterisks. Panel H, the vertical dotted lines represent the IC₅₀ of zinc pyrithione (ZPT) and zinc acetate, and show that zinc pyrithione was 89 times more potent than zinc acetate in inhibition of zidovudine-induced recA.