Table 1.
Expression of promoter-hly fusions in response to the addition of penicillin G as determined by a hemolytic activity assay
|
Hemolytic activitya | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Strain | 15b | 18b | 37c | 41b | 195d | 198c | 199c | 201c | 203d |
|
K |
10.2 ± 2.6 |
8.7 ± 1.6 |
13.2 ± 3.8 |
20.7 ± 2.5 |
30.8 ± 1.2 |
20.3 ± 1.4 |
12.2 ± 0.6 |
21.5 ± 1.3 |
19.6 ± 1.1 |
| PenG | 20.4 ± 1.9** | 13.3 ± 0.3* | 32.5 ± 4.5** | 36.1 ± 1.9** | 54.8 ± 1.8 ** | 29.5 ± 1.7* | 33.9 ± 1.6** | 28.5 ± 1.7** | 55.5 ± 3.4** |
a The hemolytic activity was measured for selected strains carrying promoter-hly fusions grown for 2 h in the presence (PenG) or absence (K) of penicillin G (0.03 μg/ml), using b0.5%, c1% or d2% suspensions of SRBC. The results are the average of three independent experiments, each performed in triplicate ± the standard deviation. Asterisks indicate significant differences according to Student’s t test (*, P < 0.05; **, P < 0.01).