FIG 2.

Iron overrides NO-induced biofilm dispersal. (A) P. aeruginosa biofilms were grown in multiwell plate batch cultures for 6 h and treated with 100 μM NO donor SP-NO and different concentrations of FeSO₄ simultaneously for 30 min before quantifying the biofilm biomass by CV staining. Each image represents the stained biofilms. Biofilms grown in multiwell plate batch cultures for 6 h and treated with 100 μM SP-NO for 15 min were subsequently treated with 100 μM FeCl₃ or FeSO₄ (B) or 200 μM PTIO (D) for 15 or 30 min before CV staining. Error bars indicate standard deviations (n = 6). (C) Effects of FeCl₃, FeSO₄, and PTIO on NO release. Levels of free NO were monitored amperometrically in a solution to which 100 μM NO donor SP-NO was added at t = 0 min. After 15 min (red arrow), 100 μM FeCl₃, 100 μM FeSO₄, or 200 μM PTIO was added to the solution. The results are representative of at least three independent experiments. *, P ≤ 0.05; **, P ≤ 0.01; ***, P ≤ 0.001 versus untreated control samples.