TABLE 2.
Catabolic repression of the PalkB promoter in strains PBS4 (wild type for cyoB) and PBS4B1 (cyoB::tet)
| Medium | Activity (repression value)a in strain:
|
Repression reliefb
|
||||
|---|---|---|---|---|---|---|
| PBS4
|
PBS4B1
|
|||||
| ME phase | LE phase | ME phase | LE phase | ME phase | LE phase | |
| Citrate | 2,500 (1) | 4,800 (1) | 2,800 (1) | 6,000 (1) | 1 | 1 |
| LB medium | 50 (51) | 70 (68) | 190 (14.7) | 670 (9) | 3.4 | 7.5 |
| Lactate | 450 (5.5) | 1,350 (3.5) | 1,000 (2.8) | 3,100 (1.9) | 2 | 1.8 |
| Succinate | 750 (3.3) | 3,000 (1.6) | 3,900 (0.7) | 6,000 (1) | 3.3 | 1.6 |
a
β-Galactosidase activities (in Miller units) in strains PBS4 and PBS4B1 at the mid-exponential (ME; A600 of 0.5) or late-exponential (LE; A600 of 1) phase of growth, growing in either LB medium or in a defined medium with citrate, lactate, or succinate as the carbon source, were obtained from Fig. 3. Repression values (indicated in parentheses) were obtained by dividing the activity observed when cells used citrate as a carbon source by that observed when LB medium, lactate, or succinate was used.
b
That is, the quotient between the repression observed in strain PBS4 and that observed in the cyo-deficient strain PBS4B1.