TABLE 2.
Among-site variation in the mutation rate
| Beneficial mutation | No.of isolates | Mutation rate |
|---|---|---|
| A1553G | 4 | 3.32E-09 |
| A1553T | 2 | 1.66E-09 |
| A1562G | 30 | 2.49E-08 |
| A1562T | 1 | 8.29E-10 |
| A1592T | 4 | 3.32E-09 |
| A455G | 7 | 5.80E-09 |
| A455T | 19 | 1.57E-08 |
| C1550T | 2 | 1.66E-09 |
| C1563G | 1 | 8.29E-10 |
| C1591T | 3 | 2.49E-09 |
| C1607T | 1 | 8.29E-10 |
The number of spontaneous rifampicin-resistant mutants carrying beneficial mutations identified in this study in a collection of 80 spontaneous rifampicin-resistant mutants that were isolated from a rifampicin-sensitive clone of P. aeruginosa PAO1 using a fluctuation test (MacLean and Buckling 2009) are shown. Any beneficial mutations not shown in this table were not found in this collection of mutants. Mutation rates at each site were calculated using an overall estimate of the mutation rate to rifampicin resistance of 6.64 × 10−8.