Fig. 3.

Serum enhances the expression of regA, pvdA, pvdS and pchR but represses the expression of bfrB in the early exponential phase of growth. PAO1 containing transcriptional or translational lacZ fusion plasmids was grown in TSB-DC or TSB-DC/ABS as described in Fig. 1. Samples were collected at the time points indicated on the graphs and the β-galactosidase activity was determined and normalized for growth (see Methods). Plasmids pRL88, pMP220 : : PpvdA, pMP220 : : PpvdS and pDH10 were utilized to examine the expression of regA (a), pvdA (b), pvdS (c) and pchR (d), respectively. Strain PW6979 : : bfrB-lacZ was used to examine bfrB expression (e). Iron was added to TSB-DC at 5 µg ml⁻¹ (TSB-DC/Fe) to induce bfrB expression as a control. Values represent the means±sem of three independent experiments. ***, P<0.001; **, P<0.01; *, P<0.05.