Liquid CAS assay. 96-well plate wells containing 200 μl unamended King's B liquid media were inoculated in triplicate from synchronized overnight cultures of the following strains: WT (black squares), acr- (white circles), pvd- (grey circles), and pvd-/acr- (grey diamonds). A triplicate media-only control (black triangles) was also included. Plates were incubated with shaking at either 22°C (A) or 28°C (B) for 48 h. Cells were then pelleted and 150 μl supernatant removed to fresh wells. CAS dye (30 μl) was added to each well and the rate at which iron was removed from the dye by secreted factors in the supernatant was followed at OD 655 (monitoring loss of blue coloration). Error bars are presented as ± 1 standard deviation.