TABLE 2.
Screening and antibiotic productivity of drug-resistant mutants
| Strain | Actinorhodin productivity (OD633)a | MIC (μg/ml)b of: | Concn of antibiotic used for screening (μg/ml) | Frequency (%) of mutants producing increased actinorhodinc | Mean productivity detected (OD633 ± SE)d | Highest productivity detected (OD633) |
|---|---|---|---|---|---|---|
| S. coelicolor 1147 (wild type) | 0.77 | Gentamicin (0.1) | 1.0 | 5 (4/80) | 1.06 ± 0.20 | 1.25 |
| Streptomycin (1.0) | 5 | 6 (7/120) | 1.17 ± 0.11 | 1.39 | ||
| Rifampin (10) | 200 | 10 (15/150) | 1.85 ± 0.21 | 2.32 | ||
| S-1 | 1.28 | Geneticin (0.2) | 2.5 | 13 (15/112) | 1.87 ± 0.17 | 2.22 |
| Gentamicin (0.1) | 2.5 | 14 (14/104) | 2.35 ± 0.35 | 2.80 | ||
| Rifampin (10) | 200 | 18 (21/116) | 2.47 ± 0.32 | 3.14 | ||
| SG-1 | 2.02 | Rifampin (10) | 200 | 10 (8/80) | 6.00 ± 0.73 | 6.88 |
a
,d The optical density of supernatant at 633 nm (OD633) was determined after 6 days of cultivation at 30°C, using a 25-ml test tube containing 5 ml of R4 medium. All measurements were done in triplicate, and the mean value is presented. Mean productivity is the mean value of the productivity of mutants producing increased actinorhodin. SE, standard error.
b
Determined after 2 days of incubation on GYM agar.
c
Mutants producing more antibiotic than starting strain. Numbers in parentheses show the number of mutants producing more antibiotic divided by the number of mutants tested.