Figure 5. The uptake and antimicrobial activity of Ga does not depend on major P. aeruginosa Fe-uptake systems.

(A) P. aeruginosa takes up Ga. WT P. aeruginosa takes up Ga in concentration-dependent manner. Isogenic strains lacking functional pyoverdine, pyochelin, pyoverdine and pyochelin, and ferric uptake systems also took up Ga. Values are mean of 4 experiments and are not statistically different from each other (P = 0.17–0.37). (B–E) P. aeruginosa strains lacking functional pyoverdine, pyochelin, pyoverdine and pyochelin, and ferric citrate uptake systems showed sensitivity to Ga’s growth-inhibitory effect that was similar to that of WT P. aeruginosa. Arrows show the final culture density obtained when WT P. aeruginosa was treated with the same concentration of Ga(NO₃)₃ (10 μM). Results are the mean of 3 separate experiments; error bars are SEM. (F) Fe-uptake mutants are sensitive to the antibiofilm effects of Ga. GFP-labeled bacteria were grown in flow cells perfused with biofilm medium without (top) and with (bottom) 1 μM Ga(NO₃)₃. Inactivation of the pyoverdine system produced biofilms with a flat structure, as described previously (11). Images were obtained after 5 days and are top-down views (x-y plane); scale bar: 50 μm. Results are representative of 3 experiments.