TABLE 4.
Proportion of E. coli mutants whose expression is RpoS and growth-phase dependenta
| Fusion type | No. of mutants with expression:
|
||
|---|---|---|---|
| Growth-phase dependent | Growth-phase independent | Total | |
| RpoS dependent | 15 | 90 | 105 |
| RpoS independent | 8 | 41 | 49 |
a
Wild-type and rpoS derivatives of rsd strains (105 total) and a randomly selected group of mutants carrying promoter-lacZ fusions whose expression is not RpoS dependent (49 total) were grown in LB broth and assayed in the exponential and stationary phases for β-galactosidase activity. A given promoter-lacZ mutation was classified as growth-phase dependent if the stationary-phase level of β-galactosidase, in an rpoS strain, was more than five times greater than that observed in the exponential-phase cultures.