FIG 4.

The ΔtctED strain (Δ) exhibits a reduced ability to grow relative to PA14 (●) when citric acid is present in M63-arginine medium. Concentrations of 0 mM (A), 2 mM (B), 10 mM (C), and 20 mM (D) citric acid were tested with zero, subinhibitory (1 μg/ml), and inhibitory (4 μg/ml) concentrations of tobramycin. The data shown are the averages from 3 biological replicates, where error bars are the standard error of the mean (SEM). Where no error bars are visible, the SEM was less than what could be displayed on the graph.