FIG. 1.

Effect of Pol IV (dinB) and Pol V (umuDC) on the dnaX36 mutator effect. All strains used were mismatch repair deficient (mutL). Mutant frequencies were determined as described in the Materials and Methods. (A) Mutant frequencies for lac G·C→T·A transversions; (B) mutant frequencies for trpE9777 reversion (−1 frameshift). The figure shows the results of one representative experiment. These experiments were performed multiple times, which yielded similar results. The dnaX⁺ strains used were NR13153, NR13157, NR13155, and NR13159. The dnaX36 strains were NR13256, NR13272, NR13258, and NR13274. The dnaX⁺ ΔumuDC strains were NR13312, NR13316, NR13314, and NR13318. The dnaX36 ΔumuDC strains were NR13276, NR13292, NR13278, and NR13296. The status of the dinB gene, chromosomal and/or episomal, in these strains is indicated in the boxes below the graph.