A and B, β-galactosidase activity was measured in M. smegmatis mc2155 containing kmtR and Pcdf fused to lacZ (in pJEM15kmtR-Pcdf) grown with no metal supplement and maximum permissive concentrations of Zn(II) (70 μm), Co(II) (15 μm), Ni(II) (35 μm), Cd(II) (75 nm), Cu(II) (50 μm), Pb(II) (10 μm), Ag(I) (0.75 μm), Bi(III) (0.75 μm), or Mn(II) (0.75 μm) (A), or up to inhibitory [Zn(II)] (B). Inset, growth (A595) of cultures against added [Zn(II)]. C, microtiter plate assays of Zn(II)-PAR formation (400 μm PAR), measured at 492 nm and zeroed against apo-PAR, as a function of [Zn(II)] in the absence (closed symbols) or presence (open symbols) of KmtR (2 μm).