Figure 7
CA439 alters IM potential and promotes colistin-mediated lysis. (a) Fluorescence intensity was monitored from a wild type strain culture incubated with 1 μM DiSC3(5) for 5 min and then with 5 μg mL−1 colistin for another 10 min followed by the indicated concentration of CA439, 25 μM CA490 or the equivalent volume of DMSO used for the maximum concentration of compound tested. Statistical analysis was performed using one-way ANOVA with Tukey’s correction multiple comparison test against no addition condition (-) (** P < 0.001; * P < 0.01; ns, no significant differences). (b) OM disruption and c, IM disruption were measured using β-lactamase assay and β-galactosidase assay, respectively, as described in Materials and Methods. Cells expressing (b) β-lactamase or (c) β-galactosidase were incubated with PBS (Saline), DMSO or increasing concentrations of CA439 (left panel) or colistin (b) from 0 to 2.5 μg mL−1 or (c) from 0 to 200 μg mL−1) in the presence of 25 μM CA439 (grey bars) or DMSO (dark bars) (right panel). (b) Nitrocefin (30 μM) or (c) ONPG (2 mM) were added as substrate and absorbance at 492 nm and 405 nm, respectively, were monitored. Statistical analysis was performed using unpaired t test (**** P < 0.0001; *** P < 0.001; ns, no significant differences). The results are the average of at least three independent experiments.
