Fig. 5. Immunogold localization of HrpZ in DC3000ΔhrpZ harbouring pMerHrpZ, which allows mercury-driven HrpZ expression. (A and B) Emergence of HrpZ (immunogold label) at the tip of the pilus 30 and 60 min, respectively, after the addition of HgCl₂ to induce HrpZ following 8 h growth in minimal medium to allow pilus formation. (C) Labelling along the proximal base of the pilus if bacteria were grown continuously in minimal medium + HgCl₂ for 8 h. Bars = 0.5 µm.