Table 1.
Antibiotic susceptibility of lpt mutant strains by the Kirby-Bauer disk diffusion testa.
| Growth inhibition halo diameter (mm)d |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Strainb | ARA (%)c | IPTG (mM)c | Sm | Ery | Rif | Novo | Tob | Ipm | Cip | Ct |
| PAO1 | 0 | 0 | 12.4 (±1.0) | 8.1 (±0.9) | 7.1 (±0.2) | 6.6 (±0.5) | 22.3 (±0.5) | 24.8 (±0.7) | 31.1 (±0.7) | 12.9 (±0.7) |
| lptH | 0.03 | 0 | 18.7 (±2.3)* | 22.3 (±2.1)** | 33.3 (±3.1)*** | 14.3 (±0.6)* | 31.7 (±2.1)** | 39.7 (±2.5)** | 44.7 (±2.3)*** | 18.0 (±1.0)* |
| 0.5 | 0 | 12.0 (±1.0) | 7.3 (±0.6) | 11.7 (±0.6)* | 7.0 (±0.0) | 23.3 (±1.5) | 24.7 (±0.6) | 27.7 (±0.6) | 12.0 (±1.0) | |
| lptE | 0 | 0 | 21.3 (±1.7)** | 17.1 (±2.4)** | 18.5 (±1.7)** | 17.0 (±1.4)** | 26.2 (±1.6)* | 28.7 (±1.9)* | 37.3 (±2.0)** | 12.9 (±0.7) |
| 0.5 | 0 | 20.2 (±1.0)* | 13.9 (±1.1)* | 18.0 (±0.8)** | 16.0 (±0.5)* | 23.7 (±1.5) | 24.7 (±0.4) | 35.8 (±1.5)* | 12.5 (±0.6) | |
| lptE 2nd | 0 | 0 | 21.5 (±1.0)** | 14.4 (±0.5)* | 30.9 (±3.8)*** | 24.8 (±1.9)*** | 33.8 (±1.3)** | 39.5 (±1.3)** | 41.8 (±1.7)** | 15.5 (±0.6)* |
| 0.5 | 0 | 19.8 (±0.5)* | 14.5 (±0.6)* | 15.8 (±1.0)* | 16.3 (±1.5)* | 25.5 (±0.6) | 25.6 (±0.5) | 35.1 (±1.3)* | 12.9 (±0.3) | |
| PAO1 pME6032 | 0 | 0 | 11.9 (±0.9) | 7.6 (±0.5) | 7.0 (±0.6) | 7.3 (±0.5) | 23.5 (±0.6) | 25.8 (±1.3) | 31.6 (±1.5) | 12.5 (±0.6) |
| lptE pME6032 | 0 | 0 | 21.7 (±0.7)** | 17.6 (±0.7)* | 18.3 (±0.7)** | 17.5 (±0.7)** | 26.6 (±0.7)* | 28.9 (±0.8)* | 39.7 (±3.5)* | 13.5 (±0.7) |
| lptE pMElptE | 0 | 0 | 21.6 (±1.1)** | 17.7 (±0.6)* | 17.7 (±0.6)* | 17.7 (±2.1)** | 27.3 (±0.6)* | 29.3 (±1.5)* | 42.0 (±2.0)** | 13.8 (±1.0) |
| 0.5 | 0 | 20.5 (±1.7)* | 15.5 (±0.9) | 18.3 (±1.3)** | 17.0 (±1.4)** | 24.5 (±1.7) | 26.8 (±1.0) | 39.3 (±1.0)* | 13.2 (±0.4) | |
| 0.5 | 1 | 15.5 (±1.3) | 8.3 (±0.6) | 10.5 (±0.6) | 8.3 (±0.6) | 23.7 (±1.5) | 24.9 (±0.9) | 34.4 (±1.8) | 12.7 (±0.4) | |
a Abbreviations: ARA, arabinose; Sm, streptomycin; Ery, erythromycin; Rif, rifampicin; Novo, novobiocin; Tob, tobramycin; Ipm, imipenem; Cip, ciprofloxacin; Ct, colistin.
b The sample lptE 2nd corresponds to the lptE conditional mutant pre-cultured in the absence of arabinose. All other conditional mutant samples were pre-cultured in the presence of 0.5% arabinose.
c Arabinose and IPTG at the indicated concentrations had no effect on the antibiotic susceptibility profile of PAO1 and PAO1 pME6032, respectively (data not shown).
d Values are the mean (± SD) of at least three independent assays. Asterisks and bold font indicate statistically-significant increases in antibiotic sensitivity with respect to PAO1 (or PAO1 pME6032): * P < 0.05, ** P < 0.01, *** P < 0.001 (Kruskal-Wallis).