Genotypes, susceptibility, and fitness of isogenic strains.

aGenotype. 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 (��araBC).dP. Statistical significance of difference in fitness relative to the wild-type (Students t-test (95% confidence limit, two-tailed P-value).eN. Number of independent competition experiments on which the fitness value is based.