Fig. 1.

Evolution of resistance against ciprofloxacin. Experiments were performed in the presence of 100 ng/ml ciprofloxacin (6.25 times MIC of the WT). (A) Frequency of ciprofloxacin-resistant populations of the Δfur genotype in comparison with the WT strain. ***P ≤ 0.001 (chi-square test using the actual number of observations). Fractions are based on a total of n = 576 populations. Error bars represent confidence intervals of proportions (Wilson procedure). (B) Survival of Δfur in the presence of ciprofloxacin compared with the WT strain. Error bars represent 95% confidence intervals. The mean of values is shown for n =3. n represents the number of repeated, independent experiments.