FIG 1.

Fitness of the evolving populations. Relative fitnesses of the different populations compared to that of the plasmid-free ancestor H. influenzae Rd KW20 (mean ± standard error of the mean [SEM]) are shown. The red dashed line represents the fitness of the parental H. influenzae Rd KW20 carrying plasmid pB1000 (Rd/pB1000). The green bars represent the relative fitnesses of the five Rd/pB1000 populations propagated in the absence of antibiotics. The red bars represent the relative fitnesses of the five Rd/pB1000A populations propagated for 10 days with ampicillin and for 10 further days without ampicillin. The dark gray bars represent the relative fitnesses of the five Rd populations propagated in the absence of antibiotics and plasmid.