TABLE 1.
Bacterial strains of E. coli used in this studya
| Strain | Genotype | Source or reference |
|---|---|---|
| P90C | ara thi Δlac-pro | 20 |
| CP55 | Δlac ΔilvA leuB::placMu9 | E. Newman |
| CV1008 | P90C ilvIH::Mu dI 1734 lrp-35::Tn10 | 18 |
| CV1216 | P90C lrp-35::Tn10 | This laboratory |
| CV1512 | CP55 lrp-35::Tn10 | This study |
| CV1513 | P90C leuB::placMu9 | This study |
| CV1514 | CV1513 lrp-35::Tn10 | This study |
| CV1517 | P90C λ Pleu att-lacZ | This study |
| CV1518 | CV1517 lrp-35::Tn10 | This study |
| CV1520 | P90C λ Pleu-lacZ | This study |
| CV1521 | CV1520 lrp-35::Tn10 | This study |
| CV1543 | P90C λ PilvIH Pleu att-lacZ | This study |
| CV1544 | CV1543 lrp-35::Tn10 | This study |
| CV1547 | P90C λ PilvIH Pleu-lacZ | This study |
| CV1548 | CV1547 lrp-35::Tn10 | This study |
| CV1549 | P90C λ P(−)ilvIH Pleu-lacZ | This study |
| CV1550 | CV1549 lrp-35::Tn10 | This study |
Strains CV1216, CV1512, CV1514, CV1518, CV1521, CV1544, CV1548, and CV1550 were created by transduction with P1 phage grown on strain CV1008, with selection for growth in the presence of 15 μg of tetracycline per ml. Similarly, strain CV1513 was formed with phage grown on strain CP55 and with 50 μg of kanamycin per ml. Strain CV1517 was constructed by amplifying region −247 to +230 from the leu operon of E. coli by PCR and cloning into plasmid pRS415 upstream of the lacZ gene (20). After transferring the leuP-lacZ fusion to λ phage by homologous recombination (20), single lysogens were identified as described earlier (24). Strains CV1520, CV1543, CV1547, and CV1549 were constructed similarly and contained the following: CV1520, 265 bp (position −247 to +18 from the leu operon); CV1543, 2,147 bp (from +50 downstream of the ilvIH promoter to +230 downstream from the leu promoter); CV1547, 1,927 bp (from position +50 downstream of the ilvIH promoter to +18 downstream from the leu promoter); CV1549, 1,840 bp (from −37 upstream of the ilvIH promoter to +18 downstream from the leu promoter).