Table 2.
The effect of the MtrC hairpin on the antibiotic susceptibility of Escherichia coli cells expressing components of the MtrCDE multidrug pump
| Constructs | Naf 1 μg | Tet 30 μg | Ery 10 μg | Nov 5 μg | Van 30 μg |
|---|---|---|---|---|---|
| pACYC-MtrCDE + pET24a | 13 ± 1 | 26 ± 1 | 21 ± 1 | 20 ± 1 | NI |
| pACYC-MtrCDE + pET24a-gIII MtrC hairpin | 9 ± 1 | 22 ± 1 | 18 ± 1 | 19 ± 2 | NI |
| pACYC + pET24a-gIII MtrC hairpin | 20 ± 1 | 36 ± 1 | 30 ± 0.1 | 20 ± 1 | NI |
| pACYC-MtrE | 15 ± 1 | 33 ± 3 | 27 ± 2 | 19 ± 1 | NI |
| pACYC-MtrE + pET24a-gIII MtrC hairpin | 15 ± 1 | 32 ± 1 | 26 ± 1 | 19 ± 1 | NI |
| pACYC MtrD | 16 ± 1 | 39 ± 3 | 30 ± 1 | 19 ± 2 | NI |
| pACYC MtrD + pET24a-gIII MtrC hairpin | 15 ± 1 | 40 ± 2 | 30 ± 1 | 20 + 1 | NI |
| pACYC Vector + pET24a | 18 ± 2 | 35 ± 2 | 32 ± 3 | 21 ± 1 | NI |
The indicated Mtr proteins were expressed from pACYC and the MtrC hairpin, with an N-terminal gIII signal sequence, from pET24a in KAM3(DE3) E. coli cells. The inhibitory zone diameter is given in mm. All disc-diffusion assays were undertaken in triplicate and the average result given. The amount of antibiotic impregnating each disc is given. Abbreviations: NI, no inhibition of growth; Naf, nafcillin; Tet, tetracycline; Ery, erythromycin; Nov, novobiocin; Van, vancomycin.