FIG 2.

Genetic modifications in the ampC promoter region of E. coli MG1655 during the acquisition of amoxicillin resistance. (a) The measured MIC as a function of the amoxicillin concentration in the culture and the mutations found in the ampC promoter sequence over the course of stepwise increasing amoxicillin concentrations for 7 replicate cultures of E. coli MG1655. For every concentration, PCR products of 2 clones were sequenced. The asterisks indicate mutations that were found only in one colony. Green color indicates mutations in the ampC attenuator region, yellow, mutations in the −10 box, blue, mutations in the interbox distance, and red, mutations in the −35 box. (b) Genomic location of the ampC promoter mutations identified during the acquisition of amoxicillin resistance in the genome of E. coli MG1655.