Fig. 7.

Response of P. aeruginosa to LAOOH and peroxynitrite. pUCp18 Ø is an empty vector, and pUCp18 ohr, ahpC1, tpx, and gpx from P. aeruginosa are vectors for ohr, ahpC1, tpx, and gpx expression, respectively. (A and B) MIC assay to assess the sensitivities of P. aeruginosa strains deficient for Cys-based peroxidases to LAOOH. (C, Upper) Western blot for Ohr expression in P. aeruginosa using an antibody against Ohr from X. fastidiosa. (C, Lower) Ponceau S was used as a loading control. Cells were exposed to SIN-1 (1 mM), DMSO (5%), LAOOH (50 μM), t-BHP (200 μM), and MeOH (5%) for 30 min at 37 °C. WT, wild type. (D) Colony count assay to assess the sensitivities of P. aeruginosa strains to SIN-1 (3 mM). In all cases, cells were treated with ATZ (5 mM), a catalase inhibitor, 10 min before cells were challenged with SIN-1 (3 mM) for 30 min at 37 °C. The bars represent the means of the colony formation unit (c.f.u.) percentage relative to the sensitivity of cells treated with DMSO (5%) + 3-ATZ (5 mM) plus SD. The Δohr mutant was statistically more sensitive than the wild-type strain (**P < 0.05, unpaired t test; n = 8). WT, wild type.