FIG. 6.

Alignment of P. aeruginosa H103 (P. aerug) and P. fluorescens OE 28.3 (P. fluor) sequence between sigX and oprF (boxed), showing the location of putative promoter sequences. Identical bases are indicated with a colon. The two transcriptional start sites, as determined from primer extension analysis (Fig. 5), are indicated with arrows, and the nucleotides (−35 and −10 sites) proposed to be associated with the SigX-dependent promoter and the SigX-independent promoter are marked with underlined italics and underlined boldface characters, respectively. The −35 site for the SigX-independent promoter proposed by Duchêne et al. (5) seems somewhat unlikely based on the lack of alignment between the P. aeruginosa and P. fluorescens sequences and the nonoptimal 20-nucleotide spacing from the −10 site, but it was not further investigated in this paper.