TABLE 1.
Bacterial strains and plasmids used in this study
| Strain or plasmid | Descriptiona | Source or reference |
|---|---|---|
| Strains | ||
| S. thermophilus | ||
| S4 | Plasmid pSt04 | BAfMb |
| S4-1 | Plasmid-cured S4 | This study |
| St11 | Recipient strain for plasmids | 23 |
| S8-1 | Plasmid-cured S. thermophilus S8 | This study |
| ER1-1 | Plasmid-cured S. thermophilus ER1 | This study |
| An55 | Isolate from yogurt, plasmid free | BAfM |
| HM69 | Isolate from yogurt, plasmid free | BAfM |
| L. lactis MG1363 | Plasmid-cured derivative of NCDO712 | 9 |
| E. coli XL1-Blue | F′::Tn10 proA+B+laclq lacZM15/recA1 endA1 gyrA96 (Nalr) thi hsdR17(rK− mK+) supE44relA1 lac | Stratagene, La Jolla, Calif. |
| Plasmids | ||
| pSt04 | Rolling-circle plasmid; repA+shsp+ | 9a |
| pAGS4E | HinPI-linearized pSt04 cloned into pBluescript II SK(+), linearized with ClaI | This study |
| pSt08 | Rolling-circle plasmid; repA+ type II R/M system | 9a |
| pHMR1 | shsp of pSt04 cloned into a 5.7-kb PstI fragment of plasmid pSt08 carrying repA and the genes for a type II R/M system | This study |
a
For all S. thermophilus strains the absence of a chromosomal copy of shsp was demonstrated by Southern blotting. Nalr, nalidixic acid resistance.
b
BAFM, Bundesanstalt for Milchforschung (Federal Dairy Research Centre) laboratory collection.