FIG. 3.
PurcA lacZ and PurcA gfpuv reporter kinetics, sensitivity, and specificity. (A) Time course of strain NJH199 β-galactosidase activity in liquid culture after induction with uranyl nitrate. The middle section of the plot, indicated by the gray region of the inset, has been removed. (B) Strain NJH199 β-galactosidase activity after 2 h of heavy metal exposure. (C) Time course of GFPuv fluorescence (expressed in relative fluorescence units [RFU] divided by the culture OD660) for strain NJH371 (PurcA gfpuv) after induction with uranyl nitrate. (D) Strain NJH371 GFPuv fluorescence after 4 h of heavy metal exposure. The error bars indicate one standard deviation from the mean; the triangles indicate the maximum and minimum observed fluorescence values. The data are aggregate results from uranyl and mock treatments (n = 7) or from replicate experiments (n = 3). (E) Inhibitory effect of high concentrations of chromium on GFPuv reporter function. Strain NJH371 was induced with 10 μM uranyl nitrate (indicated by the horizontal line at the top) with or without cadmium or chromium for 4 h before GFPuv fluorescence was assayed. The data are aggregate results obtained with 10 μM uranyl nitrate alone (n = 5) or in replicate experiments (n = 3).