Fig. 3

Changes in pyoverdine production after experimental evolution in different environments. Two mutants with deficiencies in pyoverdine production were allowed to evolve in different environments differing in their level of spatial structure (structured|unstructured) and in their iron content (“iron low”: iron chelator only; “iron med”: iron chelator + 1 μM FeCl₃; “iron high”: iron chelator + 40 μM FeCl₃). Subsequently, pyoverdine production under iron-limitation was measured for 720 evolved clones. a Clones evolved from the low-producer pvdS_gene, a mutant with a single point mutation in pvdS, encoding the iron-starvation sigma factor PvdS. b Clones evolved from the low-producer pvdS_prom, a mutant with a single point mutation in the promoter region of pvdS. Across all treatments, very few (n = 5) clones showed increased pyoverdine production. Conversely, considerably more clones (n = 29) displayed decreased pyoverdine production. Y axes show pyoverdine-specific fluorescence divided by growth (optical density at 600 nm) after 24 h of incubation. X axes show independent replicate populations the clones evolved in. Each bar represents a single measurement per evolved clone. The black line denotes the average wildtype production level in the same assay, while the blue line denotes the average production level of the respective low-producing ancestor