Figure 3.

Wild-type and apn1 mutants were exposed to aminopterin and sulfanilamide as described previously. Portions of the culture were collected prior to drug exposure, at 6 h and at 12 h, and DNA was purified as described in Materials and Methods. PCR was performed using the conditions and primers characterized by van Houten (30). PCR product was quantified using the PicoGreen assay. The amount of product PCR at a given time-point was normalized to the amount of product derived from input DNA from the pre-drug treatment DNA. Parental SSL204 is closed squares and SSL204 apn1 mutants are gray circles.