Figure 2

Susceptibilities of insertion mutants to physical and chemical stresses. E. coli cultures grown to mid-log phase were treated with 2000 μJ/cm² of UV; 2 mM H₂O₂, 10% SDS, or heat shock at 52°C for 15 min. Samples were diluted, applied to agar lacking stressor, and incubated to determine the fraction of colonies surviving. This fraction was expressed as a percent of an untreated control culture sampled at the time stress was applied. In the case of SDS, some mutants grew during treatment, which caused those samples to have values higher than the control. Values reported are the means of 3 independent experiments. Error bars indicate standard deviations of means.