FIGURE 3.

Effect of single-gene knockout mutations of hipA and clpB and their double-gene knockout mutations with relA on E. coli persister formation under ampicillin treatment. Early stationary phase cultures of W3110, ΔrelA and (A) hipA or (B) clpB knockout mutations were exposed to ampicillin (200 μg/ml) for 4–5 days at 37°C without shaking. Cells (10 or 200 μl) were removed, washed and plated to determine the persister number at the indicated time points. Data shown are from three independent experiments and error bars indicate the standard deviations.