Fig. 6

Schematic of the experimental design used to test whether copper selects for siderophore-mediated virulence. Microcosms (n = 6 per treatment) containing KB medium at a concentration of either 0.0, 0.1 or 1.0 g/L of copper sulphate (CuSO₄) were inoculated with Pseudomonas aeruginosa (either the pyoverdine producing or non-pyoverdine producing strain), incubated at 28 °C and transferred every two days into fresh media. On days two and twelve, cultures were transferred into copper free medium for 24 h before being homogenised, their per capita pyoverdine production quantified and frozen in glycerol at a final concentration of 25%. Virulence and density assays were performed using defrosted samples