Identification of the PA14_58990-PA14_59120 locus as a regulator of pil2 operon expression. (A) Localization of mariner transposon insertion inside the PA14_58990-PA14_59120 locus. (B) Expression of the ppilL2–lacZ chromosomal fusion was monitored in the PA14, Tn29, Tn114, Tn115 and Tn118 strains after 7 h of growth in LB. Corresponding β-galactosidase activities are expressed in Miller units and correspond to mean values (with error bars) obtained from three independent experiments. Wilcoxon–Mann–Whitney tests were performed, and N.S. and *** indicate to non-significant, and P < 0.001, respectively. (C) Detection of PilS2 pilin production in whole-cell extracts from PA14, Tn29, Tn114, Tn115 and T118 strains. TG1 E. coli and P. aeruginosa PA14 strains bearing the pMMBpilS2 plasmid permitting the overexpression of the pilS2 gene were used, respectively, as a positive control of a precursor and mature form of PilS2 protein. The number on the left indicates the sizes of the molecular mass standards (in kDa). Functions of the genes are listed in Supplementary Table S4.