Iron concentration is higher in the serum of TPs than that of HVs Iron concentration is higher in the serum of TPs than that of HVs. The level of iron in the sera from TPs and HVs was assessed indirectly through its binding to pyoverdine-enriched supernatant (PES) from PA14 grown in the iron-depleted medium Trypticase soy broth dialysate supplemented with 1% glycerol and 50 mM monosodium glutamate. Iron concentration is higher in the serum of TPs than that of HVs. The level of iron in the sera from TPs and HVs was assessed indirectly through its binding to pyoverdine-enriched supernatant (PES) from PA14 grown in the iron-depleted medium Trypticase soy broth dialysate supplemented with 1% glycerol and 50 mM monosodium glutamate. (A) Standard curve was prepared by adding serial dilutions of FeCl3 to PES, incubating at room temperature for 10 min, and measuring the absorbance at 460 nm. (B) Iron concentration in serum of HVs and TPs was determined by adding 100 μl of each serum to be tested to 1 ml of PES, incubating as described for panel A, obtaining the A460, and calculating the equivalent amount of iron from the standard curve. The boxes represent the median from five independent experiments, and upper and lower whiskers represent the range of distribution. *, P < 0.05. Moamen M. Elmassry et al. mSystems 2019; doi:10.1128/mSystems.00312-18