Single mutations decrease drug susceptibility and increase fitness.

aGenotype; All strains are isogenic to MG1655 and carry only the mutations shown.bMIC for ciprofloxacin (��g/ml).cFitness; Mean fitness per generation (relative to wild-type). SD, standard deviation (within parentheses) measured in pair wise competition against the isogenic wild-type.dP; Significance of fitness difference between the strains in each pair, (Students t-test, two-tailed P-value).eN; Number of independent competition experiments on which the fitness value is based.a 基因型（Genotype）：所有菌株均与MG1655为等基因株，仅携带图示的突变。 b 环丙沙星最低抑菌浓度（MIC, Minimum Inhibitory Concentration）：单位为μg/ml（原文此处存在输入乱码，已修正为标准微克每毫升单位）。 c 适应度（Fitness）：每代平均适应度（相对于野生型）；标准差（SD, standard deviation）标注于括号内，通过与等基因野生型菌株进行两两竞争实验测得。 d P值（P-value）：各配对菌株间适应度差异的显著性，采用双侧学生t检验（Student's t-test）计算得到的P值。 e 样本量（N）：该适应度数值所基于的独立竞争实验总次数。