Resistance rates observed in the fluctuation test.

**Nt is the total number of cells in the culture. #ε is the fraction of cells plated. §We counted phage-resistant colonies from 50 biological replicates for each plating environment, which were used to calculate phage-resistance rates and 95% confidence intervals (with rSalvador; see Methods). $The likelihood-ratio test statistic from rSalvador was used to determine whether each calculated phage-resistance rate is significantly different to that of the ΦX174-only plating environment. *Mutation rates and significance intervals for GM 4 μg/ml were calculated without counting plates that contained too many colonies. †Resistance rate relative to the resistance rate in the ΦX17-only plating environment, calculated for combination plating environments with chloramphenicol (CL) or gentamicin (GM). Raw data (colony counts) are provided in S3 Table. Source data for Fig 3. (XLSX)