Fig 6.

Relative growth of P. aeruginosa PAO1 biofilms in dependence of defined cation concentrations. M9 medium fully supplemented with the respective cations at the concentrations indicated was incubated overnight with or without 200 μg/ml nitroxoline. Pretreated and control media were subsequently chloroform extracted (6 by 50 ml) to remove nitroxoline and its chelates. Biofilm growth of PAO1 in control medium and in nitroxoline-pretreated medium and in pretreated medium resupplemented with the indicated cations was examined. Biofilm growth as determined by crystal violet staining was related to planktonic growth (turbidity measurement at 620 nm), with the growth ratio in the control medium taken as 1. Data represent means ± SD of three independent experiments, and significant differences to controls are indicated (*, P < 0.05; **, P < 0.01; ***, P < 0.001).