Fig 1.

Growth-promoting activity of deferiprone. (A) Growth of P. aeruginosa PAO1 at 37°C in aerated 50-ml flasks containing 10 ml of M9-S supplemented with increasing deferiprone (DFP) concentrations (open symbols, left ordinate). Relative pyoverdine (PVD) levels were determined after 24 h of growth and are expressed as optical densities at 405 nm (OD₄₀₅) of the bacterial culture supernatant normalized to the OD₆₀₀ of the culture (filled symbols, right ordinate). (B) Growth response of wild-type P. aeruginosa PAO1 (WT) and of the ΔpvdA ΔpchD double mutant to iron starvation, and effects of different iron chelators on the growth of the ΔpvdA ΔpchD double mutant. M9-S was supplemented with 2,2′-dipyridyl (DIP; 400 μM) or FeCl₃ (Fe[III]; 50 μM) to compare the responses to reduced or increased iron availability of the wild type and the siderophore null mutant. The growth-promoting activity of pyoverdine (PVD), pyochelin (PCH), deferoxamine (DFO), and deferiprone (DFP) was assessed by adding 20 μM each compound to M9-S. Cell density (OD₆₀₀) was measured after 12 h of growth at 37°C in 96-well microtiter plates containing 200 μl of culture medium. An overnight P. aeruginosa culture in M9-S was used as the inoculum upon dilution at an OD₆₀₀ of ∼0.01. Each value is the mean of eight independent measurements ± the standard deviation.