TABLE 1.
Bacterial strains and plasmids
| Strain or plasmid | Characteristics | Source or reference |
|---|---|---|
| Strains | ||
| E. coli | ||
| EC101 | Derivative of E. coli with pWV01 RepA integrated into the chromosome | 16 |
| DH5α | supE44 Δlac U169 (φ80lacZΔM15) R17 recA1 endA1 gyrA96 thi-1 relA1 | Gibco-BRL |
| X10Gold | Ultracompetent cells | QuikChange XL site-directed mutagenesis kit |
| L. monocytogenes | ||
| EGDe | Wild-type strain, serotype 1/2a | W. Goebel |
| LO28 | Wild-type strain, serotype 1/2c | P. Cossart |
| EGDe-pHS1::htrA | EGDe derivative with pHS1 inserted in htrA | This study |
| EGDe-htrA-rev | EGD-pHS1::htrA with pHS1 cured from the chromosome | This study |
| HtrASS* | EGDe derivative with a frameshift mutation in the −73 to −74-bp region of the putative signal sequence of htrA | This study |
| LO28Δlisk | LO28 with a 498-bp deletion in lisK | 4 |
| Plasmids | ||
| pORI19 | EMr, Ori+, RepA− derivative of pOR128 | 16 |
| pVE6007 | CMr, temperature sensitive, RepA+ derivative of pWV01 | 18 |
| pKSV7 | CMr, temperature sensitive | 29 |
| pHS1 | pORI19 containing 721-bp region central to htrA | This study |
| pHS2 | pKSV7 containing 797-bp region incorporating both potential start codons of htrA | This study |
| pHS3 | pKSV7 containing the desired frameshift mutation in the 797-bp region of htrA | This study |