Figure 4. Evolutionary trajectories of iron metabolism in the CF airways.

Following infection (n = 45 clonal lineages of 33 clone types), pyoverdine production is frequently upregulated (n = 25). Cheaters are significantly more likely to invade following upregulation. Following loss of pyoverdine production in the social environment (n = 26 non-producing clonal lineages of 6 clone types, from eight independent losses of production and two clonal lineages from which no pyoverdine producers were sampled), the phu system is frequently upregulated by intergenic phuS//phuR mutations (15 times), while this very rarely occurs (one time) when pyoverdine is produced in the social environment (n = 47 producing clonal lineages of 32 clone types).