Fig. 2.

D424A I709N A759R Pol I achieves efficient and preferential mutagenesis, and mutagenesis is sensitive to culture conditions. JS200 cells transformed with a plasmid expressing Pol I and a plasmid encoding the β-lactamase reporter were grown under “initial” or “optimized” conditions as described in Materials and Methods. The plot represents carbenicillin (as an indicator of plasmid mutagenesis, solid columns) or rifampin resistance (as a readout for chromosomal mutagenesis, white columns) as a function of different Pol I low-fidelity mutants. Each point was plated in triplicate, and error bars represent standard error of the mean (P < 0.05).