Expression levels of the isc operon in response to stresses.

(A) Analysis of the iscR expression during normal growth and in response to oxidants after inducing the culture with 1 mM H₂O₂, 1 mM CuOOH, 1 mM tBOOH, 0.5 mM paraquat, 0.5 mM menadione, 0.5 mM plumbagin, 0.1 mM NEM, 1 mM dipyridyl, 0.5 M NaCl, 0.5 M KCl, LB medium without NaCl (low salt) without (UN) and 0.5 mM paraquat for 15 min under aerobic and anaerobic conditions supplemented with nitrate (+KNO₃). (B) and (C) show the expression profiles of iscR and fdx2, respectively, in uninduced (grey bars) and 0.25 mM plumbagin-induced (closed bars) cultures of P. aeruginosa PAO1 and ΔiscR mutant harbouring pBBR1MCS-4 plasmid (vector), plasmid expressing wild-type IscR (WT), and mutated IscR (C92A, C98A, C104A, H107A, E43A, or C111A). qRT-PCR was performed as described in the Methods. The data are presented as the means ± SD from three independent experiments. The relative expression was analysed using the 16S rRNA gene as the normalising gene and expressed as fold expression relative to the level of the uninduced PAO1.