FIG. 3.

Spontaneous mutation frequencies observed in E. coli multiple mutants lacking oxidized pyrimidine- and purine-specific DNA glycosylases. Mid-log-phase cultures were plated on Luria-Bertani medium with and without 100 μg of rifampin per ml and incubated for 15 h at 37°C. Mutants per 10⁸ cells are shown. The data represent the average of the three experiments summarized in Table 1. W.T., wild type.