Fig 4.

(A) Protease activity, (B) elastase activity, and (C) PQS/HHQ levels, normalized to cell density (OD₆₀₀), in the supernatants of P. aeruginosa PAO1 and the apaH mutant, carrying or not the pMEapaH plasmid, cultured at 37°C in LB, supplemented with 100 μM IPTG in the case of ΔapaH pMEapaH. (D) Growth curves and (E) pyoverdine levels, normalized to cell density (OD₆₀₀), of the same strains cultured at 37°C in the iron-poor medium CAA, supplemented with 50 μM FeCl₃ when indicated (+ Fe), and 100 μM IPTG in the case of ΔapaH pMEapaH. Values are the mean (± standard deviation) of at least three independent assays. Asterisks indicate a statistically significant difference (P < 0.001) with respect to PAO1 (ANOVA). The control strains with the empty plasmid pME6032 are shown in S6 Fig.