TABLE 1.
Strain characteristics as a function of mcr-1 transcription levela
| Strainsb | Description | Promoter sequence | mRNA levelc Mean ± SD |
Relative growth rated Mean ± SD | Colistin MICse |
Protein levelf Mean ± SD |
NPN uptake [%]g Mean ± SD |
|---|---|---|---|---|---|---|---|
| K12 (DA5438) | MG1655 | 1.00 ± 0.01 | 0.125 | 0.04 ± 0.02 | 0 ± 0.72 | ||
| QH0001 | J23213-mcr-1 | 5′-CTG ATG GCT AGC TCA GTC CTA GGG ATA GTG CTA GC-3′ | 0.7 ± 0.22 | 0.98 ± 0.01 | 0.25 | 0.34 ± 0.06 | −0.35 ± 0.34 |
| QH0002 | J23112-mcr-1 | 5′-CTG ATA GCT AGC TCA GTC CTA GGG ATT ATG CTA GC-3′ | 1.4 ± 0.78 | 0.98 ± 0.01 | 0.5 | 0.48 ± 0.18 | 0.23 ± 0.41 |
| QH0003 | J23113-mcr-1 | 5′-CTG ATG GCT AGC TCA GTC CTA GGG ATT ATG CTA GC-3′ | 2.5 ± 0.69 | 0.98 ± 0.02 | 1 | 0.51 ± 0.42 | 0.13 ± 0.54 |
| QH0004 | J23117-mcr-1 | 5′-TTG ACA GCT AGC TCA GTC CTA GGG ATT GTG CTA GC-3′ | 10.0 ± 2.37 | 0.98 ± 0.01 | 4 | 0.83 ± 0.45 | 0.12 ± 0.63 |
| QH0005 | J23115-mcr-1 | 5′-TTT ATA GCT AGC TCA GCC CTT GGT ACA ATG CTA GC-3′ | 102.6 ± 66.05 | 0.97 ± 0.01 | 8 | 1.29 ± 0.27 | 0.86 ± 0.35 |
| QH0006 | J23105-mcr-1 | 5′-TTT ACG GCT AGC TCA GTC CTA GGT ACT ATG CTA GC-3′ | 177.8 ± 96.50 | 0.98 ± 0.01 | 8 | 3.14 ± 0.57 | 0.90 ± 0.14 |
| QH0007 | J23110-mcr-1 | 5′-TTT ACG GCT AGC TCA GTC CTA GGT ACA ATG CTA GC-3′ | 185.7 ± 34.28 | 0.88 ± 0.02 | 8 | 7.96 ± 2.64 | 16.69 ± 0.36 |
| E. coli 08-85 | mcr-1 carrying | NA | 33.96 ± 11.74 | ND | 4 | ND | ND |
| E. coli 13-66 | mcr-1 carrying | NA | 24.76 ± 8.53 | ND | 8 | ND | ND |
| E. coli 13-43 | mcr-1 carrying | NA | 16.95 ± 3.63 | ND | 8 | ND | ND |
NA, not applicable; ND, not determined.
QH0001 to QH0007 are constructs isogenic to MG1655 with the mcr-1 gene being placed downstream of J23-series promoters in the galK locus. E. coli 08–85, E. coli 13–66, and E. coli 13–43 are clinical mcr-1-carrying strains.
mRNA levels of mcr-1 relative to control genes hcaT and cysG, with standard deviations.
Exponential growth rates relative to E. coli K12 with standard deviations; the experiment was conducted three times on different days, and representative results from one experiment are shown.
MICs of colistin against E. coli 08–85, E. coli 13–66, and E. coli 13–43 were determined previously (13).
MCR-1 protein levels quantified by western blot band intensity analysis with a densitometer (n = 3).
NPN uptake rates with 0.1% Triton X-100-treated cells set as the 100% NPN uptake control.