Induction of gene expression by divalent cations. The reporter lacZ gene expression driven by promoters Pczr and Pncz was evaluated by β-galactosidase activity assays in the presence of different divalent cations. The results shown are the average of at least three experiments. Error bars indicate standard deviations. Metal concentrations were: CdCl2, 10 μM; ZnCl2, 100 μM; CoCl2, 100 μM; NiCl2, 100 μM. Asterisks indicate results significantly different than those of of the same time points without metal (p ≤ 0.05).