Figure 2

Detection of allele conversion between mutL and 6bpΔ mutL by PCR and electrophoresis. (A) S. typhimurium LT7 mutator strain 9052D1, showing a strong tendency for 6bpΔmutL cells to become mutL cells once the nutrition stress was removed. (B) Auxotrophic strain 9052D1 Tyr-, showing an obvious tendency for mutL cells to become 6bpΔmutL cells soon after inoculation into a stressful environment; SGSC1417 and SGSC1412, no allele conversion detected. Lanes 1-12, PCR products of mutL (shown as a 136-bp fragment) or 6bpΔmutL (shown as a 130-bp fragment) alleles in cells of bacterial cultures on days as indicated; lane 13, 136-bp size marker; lane 14, 130 bp size marker.