TABLE 1.
β-Lactamase induction and murein turnover in LT deletion mutants of E. coli harboring pJP1 (ampC+ ampR+)
| Strain (ΔLT) | β-Lactamase activity (pmol/min × mg of protein)a
|
Murein turnover
|
|||
|---|---|---|---|---|---|
| Uninduced | Induced | Induction factorb | Muropeptides released (%)c | Decrease in turnover (%)d | |
| MC1061 (wild type) | 34 | 400 | 12 | 68 | 0 |
| MUF16 (ΔSlt70) | ND | ND | 67 | 2 | |
| LT12 (ΔMltA) | 42 | 330 | 8 | 60 | 13 |
| MUF33 (ΔMltB) | 30 | 180 | 6 | 57 | 16 |
| MUF45 (ΔMltA/MltB) | 26 | 75 | 3 | 42 | 38 |
| LT60 (ΔSlt70/MltA) | ND | ND | 56 | 19 | |
| MUF49 (ΔSlt70/MltB) | ND | ND | 47 | 31 | |
| MUF61 (ΔSlt70/MltA/MltB) | ND | ND | 19 | 72 | |
a
β-Lactamase activity was determined in crude cell extracts by following the hydrolysis of nitrocefin in a photometer at 492 nm as described in detail in Materials and Methods. The values are averages of four independent experiments. The average standard deviation was less than 2%. ND, not done.
b
Quotient of β-lactamase activity of uninduced and induced cells.
c
Decrease in radioactivity in SDS-insoluble material after growth for 135 min in the absence of label (chase). The cells had been prelabeled with [3H]GlcNAc as described in detail in Materials and Methods.
d
Relative to the turnover of the wild type (100%).