Pi efflux from stationary phase cells exposed to copper. 48 h MT + P cells of the indicated strains were resuspended in T buffer and exposed to 0.25 mM Cu2+ for the indicated times. Pi was quantified in supernatants as described in Methods. Data are expressed as average ± SD of four independent experiments. Different letters indicate significant differences according to Tukey’s test with a p-value of 0.05.