Inhibition of DAPI efflux activity by thymoquinone by different bacteria. Various concentrations of thymoquinone were added, and the mixture was preincubated with the cells for 5 min. Glucose (final concentration, 20 mM) was added to initiate the assay. The relative initial velocity of DAPI efflux was measured. The initial velocity observed in the absence of Thymoquinone was set at 100%. Dotted lines indicate IC50.