FIG 1.

Selection of resistance in E. coli exposed to rifampin or the drug degradation product rifampin quinone. E. coli were cultured in a range of concentrations of either RIF (a) or the drug degradation product RFQ (b) with 2-fold increments of doses. Each day, bacteria were selected from the concentration that inhibited growth by approximately 50% (IC₅₀; red circles), diluted in fresh media, and aliquoted to a fresh range of drugs. All experiments were conducted in triplicate, with each heatmap corresponding to the top dose-response curves. The right shift in dose-response curves over time demonstrates that E. coli acquire up to a 14-fold increase in IC₅₀ after exposure to rifampin (a) and a 32-fold increase in MIC after exposure to rifampin quinone (b).