TABLE 3

Spontaneous Lac+ revertants per 108 cells

Base substitutionsFrameshifts
Episome from:Reversion eventssExo+ssExoRel. freq/(Exo/Exo+)Episome from:Reversion eventssExo+ssExoRel. freq.(Exo/Exo+)
CC101AċT→CċG1.30.510.39CC107+1G423007.2
CC102GċC→AċT1.21.71.42CC108−1G5091018
CC103GċC→CċG0.500.400.82CC109−2GC1101601.5
CC104GċC→TċA1.81.40.77CC110+ 1A1.47.25.2
CC105AċT→TċA0.760.400.48CC111−1A6.0559.3
CC106AċT→GċC0.640.380.60
  • STL3679-STL3689 (ssExo+) and STL3618-STL3628 (ssExo; ExoI ExoVII RecJ) carry F′ episomes derived from the indicated strain, each with a different mutant version of lacZ. These Lac strains can revert to Lac+ by a mutation of the specified type, as described (materials and methods; Cupples et al. 1990). Reported frequencies for each strain are the average of at least five independent assays, as described in materials and methods.