FIG. 5.

Primer extension analysis of transcriptional start sites immediately upstream of oprF in wild-type (H103) (SigX+) and sigX mutant (H814) (SigX−) P. aeruginosa. Cells were harvested from high-salt LB broth at mid-log phase. The band corresponding to a SigX-dependent transcriptional start site is marked −40, indicating the start site’s position upstream of the initiation codon of oprF. The band corresponding to the SigX-independent start site is at location −57 from the start of oprF. The cutting and pasting for this figure was necessitated by the fact that it required different exposure times to optimally visualize the sequencing ladder (G, A, T, C) and primer extension products.