TABLE 1.
tnaA-lacZ expression observed in various strains with the changes indicated, and their duplication times
| 23S rRNA gene mutation | tnaA-lacZ inductiona | Duplication time (min)b |
|---|---|---|
| None | + | 66 |
| +A751 | − | 78 |
| A2587C | + | 82 |
| A2587G | + | 72 |
| U2586C | + | 73 |
| U2586G | + | 75 |
| U2584C | − | 83 |
| G2583A | − | 85 |
| U2609C | − | 90 |
The SR-14 strain was transformed with plasmids containing each of the 23S rRNA genes indicated in the table and were grown on Vogel and Bonner (26) minimal agar plates supplemented with 0.2% glycerol, 0.05% ACH, 100 μg/ml l-Trp, and 40 μg/ml of the color-producing substrate X-Gal at 37°C for 16 h. The presence (+) or absence (−) of blue in the colonies indicated whether synthesis of β-galactosidase by the reporter gene fusion, tnaA-lacZ, was appreciably induced by l-Trp.
Cell growth of each strain in Vogel and Bonner (26) minimal medium supplemented with 0.2% glycerol and 0.05% ACH at 37°C was determined by measuring cell density using a Klett colorimeter equipped with a 660-nm filter, every hour. The duplication times shown were calculated using the log phase growth data obtained for each strain.