FIG 1.

Copper sensitivity of A. baumannii strains in liquid culture. Strains were grown with shaking at 37°C for 6 h in M9 medium supplemented with the indicated concentrations of CuSO₄. Bacterial growth was measured by OD₆₀₀ measurement (A, C, E, G, I, K, and M) and colony enumeration (CFU per milliliter) (B, D, F, H, J, L, and N). The data are presented as geometric means and SEM for three biologically independent experiments. E. coli K-12 MG1655 was included as a positive control (M and N). At each time point, growth in the presence of each copper concentration was compared to that of the 0 μM control by two-way ANOVA with Tukey's adjustment for multiple comparisons. The symbols above the graphs indicate which copper treatments were statistically significantly different (P < 0.05) from the 0 μM control, as follows: ∼, growth in 1.5 mM CuSO₄ was different from the control; +, growth in 1 mM and 1.5 mM CuSO₄ was different from the control; *, growth in 500 μM, 1 mM, and 1.5 mM CuSO₄ was different from the control; #, growth in 250 μM, 500 μM, 1 mM, and 1.5 mM CuSO₄ was different from the control; and ∧, growth in 100 μM, 250 μM, 500 μM, 1 mM, and 1.5 mM CuSO₄ was different from the control.