Table 1.

Frequencies of the appearance of spontaneous mutants resistant to streptomycin and/or rifampin inM. smegmatisa

StrainMutation frequency with drug
Wild typeStr* Rif*
 mc26>2 × 10−4 >2.4 × 10−5
StrrmutantRif* Rif + Str*
 R43L>4.5 × 10−5 9.0 × 10−7
 N43L>2.5 × 10−5 4.2 × 10−8
RifrmutantStr* Str + Rif*
 R526H>2 × 10−3 2.5 × 10−7
 Y526H>4 × 10−4 5.5 × 10−8
  • a The frequencies of the appearance of resistant mutants are relative to the total CFU plated. Str, streptomycin; Rif, rifampin; ∗, selective medium contains the indicated drug.