FIG. 5.

OxyR- and SoxRS-independent induction of the isc operon. (A) Structure of the isc operon and sequence of the yfhP promoter. The induction ratios observed for the wild-type and ΔoxyR mutant strains in the microarray experiment are given below each gene. The yfhP transcription start is marked by the black arrow, and the start of the corresponding ORF is denoted by a white arrow. (B) Primer extension assays of yfhP expression in wild-type (MC4100), ΔoxyR (GSO47), ΔsoxRS (GSO71), and Δfur (GSO72) strains grown in LB medium. Exponential-phase cultures were split into two aliquots: one aliquot was left untreated, and the other was treated with 1 mM hydrogen peroxide. The cells were harvested after 10 min, total RNA was isolated, and primer extension assays were carried out with primer 686 specific to yfhP. The neighboring sequencing reactions were carried out with the same primer.