TABLE 3.
Resistance of E. coli mutant strains to cadmium and zinca
| Relevant genotype | Zn2+
|
Cd2+
|
||
|---|---|---|---|---|
| MIC (μM) | IC50 (μM) | MIC (μM) | IC50 (μM) | |
| Wild type | 1,400 | 859 ± 95 (85 ± 9) | 900 | 572 ± 80 (109 ± 15) |
| ΔrpoE | 1,100 | 616 ± 64 (136 ± 14) | 300 | 248 ± 7 (91 ± 3) |
| ΔzntA | 600 | 366 ± 21 (94 ± 5) | 40 | 12 ± 4 (6 ± 2) |
| ΔzitB | 1,400 | 899 ± 129 (94 ± 13) | 900 | 546 ± 68 (123 ± 15) |
| ΔrpoE ΔzntA | 600 | 206 ± 24 (43 ± 5) | 40 | 6 ± 0 (1.3 ± 0.1) |
| ΔzntA ΔzitB | 600 | 201 ± 11 (76 ± 4) | 40 | 16 ± 3 (8.2 ± 1.7) |
| ΔrpoE ΔzitB | 1,100 | 545 ± 107 (83 ± 16) | 300 | 78 ± 26 (86 ± 29) |
| ΔrpoE ΔzntA ΔzitB | 400 | 118 ± 1 (20 ± 0) | 40 | 11 ± 1 (8.6 ± 1.0) |
a
MICs were determined on LB medium after 16 h at 37°C. The IC50 is the zinc or cadmium concentration required to decrease the turbidity at 600 nm of the growing cells to half of that of the positive control value (no added zinc), as shown for copper in Fig. 1. The number in parentheses following the IC50 value is slope b of the sigmoidal dose-response curve.