FIG. 1.

(A) Schematic diagram of the ptxS upstream region. The locations of the potential promoter region, the 52-bp fragment, the 14-bp palindromic sequence, and the essential restriction sites are indicated. The 5′ end of the ScaI site is located 9 bp 3′ of the ptxS translation start codon, while the 3′ end of the KpnI site is located 7 bp 5′ of the ptxS translation start codon. (B) Localization of the ptxS promoter activity. DNA fragments that carry the indicated deletions from the 5′ end of the ptxS upstream region were synthesized by PCR and cloned into the lacZ fusion vector pSW205 (14). Recombinant plasmids were introduced into the P. aeruginosa strains PAO1 and PAO::ptxS, and the level of β-galactosidase activity was determined as previously described (10). Values are the averages of results of three independent experiments ± the standard errors of the means.