Fig. 1

Evolved clones of P. aeruginosa show impaired growth and pyoverdine production. a Schematic representation of pvdS regulation under iron-poor and iron-rich conditions. When iron is limited, pvdS is transcribed and upregulates pyoverdine biosynthesis. When iron levels in the cytoplasm are sufficient, Fur (ferric-uptake regulator) builds a complex with Fe²⁺, which then binds to the pvdS-promoter site and inhibits transcription. Stars indicate SNPs in the mutant strains pvdS_prom (red) and pvdS_gene (blue). b and c A P. aeruginosa wildtype strain (PAO1 wt) and three different mutants with deficient pyoverdine production were grown in iron-limited media at 37 °C for 24 h. Y axis shows (b) optical density measured at 600 nm or (c) pyoverdine-specific fluorescence (emission|excitation 400 nm|460 nm). X axis shows time in hours. ΔpvdD: engineered knock-out mutant carrying an in-frame deletion of pvdD, encoding a non-ribosomal peptide synthetase, part of the pyoverdine synthesis pathway. pvdS_gene: evolved mutant with single point mutation in pvdS, encoding the iron-starvation sigma factor PvdS. pvdS_prom: evolved mutant with a single point mutation in the promoter region of pvdS. Graph depicts means and standard errors based on four independent replicates per strain