(A) PlcH is secreted in a tat mutant of the PAO1 strain complemented with the tat operon of E. coli. PlcH activity is expressed relative to the extracellular activity of the PAO1 strain expressing wild-type PlcH, which was set to 1 (bar 1). Bar 2, PAO1Δtat mutant expressing wild-type PlcH; bar 3, PAO1Δtat mutant expressing wild-type PlcH complemented with vector alone; bar 4, PAO1Δtat mutant expressing wild-type PlcH complemented with the tat operon of E. coli; bar 5, PAO1Δtat mutant expressing wild-type PlcH complemented with the tat operon of P. aeruginosa. Error bars indicate standard errors of the means of three independent experiments. (B) Secretion of pyoverdine in a PAO1 tat mutant complemented with the tat operon of E. coli. Lane 1, PAO1; lane 2, PAO1Δtat mutant; lane 3, PAO1 Δtat mutant complemented with the tat operon of P. aeruginosa; lane 4, PAO1 Δtat mutant complemented with vector alone; lane 5, PAO1 Δtat mutant complemented with E. coli tat operon; lane 6, PAO1 ΔtatC mutant complemented with E. coli tat operon; lane 7, PAO1 ΔtatC mutant.