Resistance of the Δfur mutant strains to transition metals. Dose-response experiments were performed with parent strain AE104 (closed circles; n = 6 or 7) and its ΔfurA (open squares; n = 6), ΔfurB (open triangles; n = 6), ΔfurC (open circles; n = 8), and ΔfurBC (gray triangles; n = 5 or 6) mutant strains in the presence of zinc (A), cadmium (B), or cobalt (C). Deviation bars are shown.