Table 5

Direct determination of relative fitness costs of lowest-fitness-cost Myx-resistant mutants and zero-fitness-cost Rif-resistant mutant

Myx-resistant mutant (RNAP subunit and mutation)aRif-resistant mutant (RNAP subunit and mutation)aRelative fitness cost of Myx resistance vs Rif-resistance (% per generation [± SEM])
Predicted valuebObserved valuec
β 1127 (1322) Ser → Proβ 481 (526) His → Asn5 (±4)6 (±2)
β′ 925 (917) Thr → Lysβ 481 (526) His → Asn8 (±3)8 (±1)
  • a Residues are numbered as in S. aureus RNAP and, in parentheses, as in E. coli RNAP.

  • b Predicted relative fitness costs are calculated as the fitness cost of the Myx-resistant mutant (Table 3) minus the fitness cost of the Rif-resistant mutant (Table 4).

  • c Observed relative fitness costs are from pairwise-competition fitness assays directly comparing the Myx-resistant mutant and the Rif-resistant mutant.