FIG 6.

Accumulation of compound A and rifampin in E. coli tolC mutant. (A) A time-dependent increase (0 to 40 min) in the intracellular concentration of compound A was observed in the E. coli tolC mutant upon treatment with 6.25 μM compound A. No significant change in the intracellular concentration was observed upon similar treatment in E. coli WT cells. Concentrations in the wash control samples were used to measure nonspecific binding to the cell matrix. The difference between the wash control concentration and the concentration of treated samples was considered to represent the intracellular concentration.

$$\text{Fold change in}\hspace{0.17em}[\text{Compound A}]=\frac{\text{Intracellular}\hspace{0.17em}[\text{Compound A}]\hspace{0.17em}\text{nM at time}\hspace{0.17em}t}{\text{Intracellular}\hspace{0.17em}[\text{Compound A}]\hspace{0.17em}\text{nM at time}\hspace{0.17em}0}$$

(B) Intracellular concentrations of rifampin observed in E. coli (Eco) tolC mutant and E. coli WT cells upon treatment with 2 μg/ml rifampin for 40 min were not significantly different.