TABLE 2.
MICs of copper for E. coli strain GR1 mutant derivatives in LB medium (pH 7.5) containing copper sulfate
| Bacterial strain | Relevant genotype | Complementing gene in trans | MIC (mM) of CuSO4a |
|---|---|---|---|
| GR1(pASK-IBA3) | ΔcueO | None | 3.0 |
| EC933(pASK-IBA3) | ΔcueO ΔcusF | None | 1.25 |
| EC933(pECD735) | ΔcueO ΔcusF | cusF | 2.25 |
| EC933(pECD736) | ΔcueO ΔcusF | cusF (M69I-M71I) | 1.25 |
| EC933(pECD775) | ΔcueO ΔcusF | cusF (M69I) | 1.5 |
| EC933(pECD776) | ΔcueO ΔcusF | cusF (M71I) | 1.5 |
| EC933(pECD737) | ΔcueO ΔcusF | cusF (H25R-H26R-H27R-H57R-H58R) | 1.0b |
| EC933(pECD766) | ΔcueO ΔcusF | cusF (H57R-H58R) | 1.75 |
| EC933(pECD763) | ΔcueO ΔcusF | cusF (H57Q-H58Q) | 2.0 |
| EC933(pECD764) | ΔcueO ΔcusF | cusF (H25Q-H26Q-H27Q) | 2.25 |
| EC933(pECD765) | ΔcueO ΔcusF | cusF (D48N) | 2.25 |
| EC933(pECD762) | ΔcueO ΔcusF | cusF (F73Y) | 2.25 |
The MIC is defined as the lowest concentration at which no growth was observed. Strains were grown overnight and diluted 1:500 into fresh LB medium. After 2 h of growth at 37°C they were plated onto LB agar, carefully adjusted to pH 7.5 with NaOH, containing different concentrations (0.5 to 4.0 mM in steps of 0.25 mM) of CuSO4. LB agar plates for complementation experiments contained anhydrotetracycline (200 μg/liter) to induce expression of complementing genes. Growth was monitored after 16 h at 37°C. All experiments were done at least three times with identical results.
Reduced plating efficiency was also observed on LB agar plates containing anhydrotetracyline without CuSO4.