Figure 4.

Rates of DNA synthesis in dnaE486 polB⁺/ΔpolB strains. The ability of cells to replicate their DNA was measured essentially as described in Fig. 2. The only difference is that the initial DNA synthesis was at 30°C. Where noted, some cells were shifted to the nonpermissive temperature of 43°C. (A) RW620 (dnaE486polB⁺) unirradiated at 30°C (▾); irradiated at 30°C (●); unirradiated at 43°C (▿); and irradiated at 43°C (○). (B) RW622 (dnaE486ΔpolB) unirradiated at 30°C (▾); irradiated at 30°C (●); unirradiated at 43°C (▿); and irradiated at 43°C (○). The experiment from which the data were plotted was repeated four times and is reproducible. The rapid resumption of replication followed by the steep decline in incorporation observed at nonpermissive temperature in the dnaE486polB⁺ strain, shown in A, was observed in each of the repeat experiments.