Figure 1. Tellurite-induction of β-galactosidase activity in E. coli reporter strains.

E. coli reporter strains ADA100 [AB734 λΦ(ibp::lacZ)], ADA310 [AB734λΦ (cspA::lacZ)], ADA410 [AB734 λΦ(p3RpoH::lacZ)] and ADA510 [AB734 λΦ(sulA::lacZ)] containing the stress-responsive promoters ibpA, cspA, p3RpoH and sulA fused to the lacZ gene respectively, were used to study transcription induction in cells treated or untreated with K₂TeO₃ (0.5 µg/ml). β-galactosidase activity was evaluated at time 0 and after 3 h with or without tellurite treatment. The fold induction was calculated dividing the value obtained at 3 h by the value at time 0. Results are the average of at least 4 determinations.