Fig. 4.

The genes involved in enterobactin biosynthesis and tolC are required for Cu-resistance. (a) WebArrayDB analysis for ent and tolC loci done in SLB or M9 medium in the presence of Cu ions as described in Fig. 1. (b) β-galactosidase activity from a strain carrying an entE : : MudJ transcriptional fusion cultured overnight in LB or M9 without (–) or with the addition of CuSO₄ (Cu), FeSO₄ (Fe) or both metal salts (Fe+Cu). The metal salts were used at a final concentration of 250 µM in LB or 10 µM in M9. The data correspond to mean values of four independent experiments performed in duplicate. Error bars depict standard deviations. (c) The final OD₆₃₀ of the cultures of the wild-type strain (WT) or the mutants in the indicated genes was recorded after 15 h of incubation in the presence of the specified concentrations of CuSO₄. Data correspond to mean values of three independent experiments performed in triplicate. Error bars depict standard deviations.