Fig. 1.

Susceptibility of E. coli BL21 (DE3) expressing GusA as a control (Gus), GlNR1 (NR1), and GlNR2 (NR2), two GusA (Gus/Gus), or both nitroreductases (NR1/NR2) to metronidazole (MET) and to nitazoxanide (NTZ). Tetracycline (TET) was included as a positive control. Plates with different cell lines exposed to discs containing the drugs were incubated under aerobic (A) or semi-aerobic (B) conditions. After 24 h, diameters of inhibition zones were determined. Mean values ± SE are given for 3 replicates. Values marked by asterisks are significantly different from the controls, i.e. to Gus for the single transformants and to Gus/Gus for the double transformant (paired t-test, two-sided, *p < 0.01).