FIGURE 3.

The trxR gene product contributes to oxidative stress resistance of A. fumigatus. (A) Growth inhibition by H₂O₂ correlates with increasing concentrations of doxycycline as monitored by halo formation in agar diffusion tests (left panel, plate assays; right panel, quantification from three replicates). (B) Transcription of trxR in the wild-type isolate AfS35 is not significantly influenced by oxidative stress conditions as triggered by 5 mM H₂O₂, whereas trxR transcript levels increase upon prolonged incubation of AfS227 in the presence of the oxidative stressor. All samples were generated from mycelia grown in the absence of doxycycline to exclude interference with trxR transcription in the TetOFF strain. (C) Oxidative stress resistance is influenced by metronidazole in a trxR-dependent manner, as deduced from a positive correlation of H₂O₂ sensitivity with increasing metronidazole concentrations for the conditional tetOFF:trxR expression strain AfS227.