A spectrophotometric method to determine the siderophore production by strains of fluorescent Pseudomonas in the presence of copper and iron

A simple procedure to determine levels of siderophore production by strains of Pseudomonas, particularly the Avm strain is described. Bacterial cells were incubated for 24 h in iron-rich (RM) and iron-limiting conditions (RM-Fe) with and without 6 and 60 μM of CuSO4. Cells grown under iron-limiting conditions developed a green color even in the presence of Cu. The spent media supernatants from the Avm cells grown in RM-Fe medium showed a maximum peak of absorbance at 400 nm, which suggest that this strain produced a single type of siderophore. The presence of 60 μM of CuSO4 in the cultures did not interfere with the detection of siderophores in the spent media. Clear supernatants obtained from cultures of 10 fluorescent Pseudomonas were diluted 1 to 10 in deionized water and the absorption at 400 nm was determined. The results demonstrated the clear discriminating capacity of this highly practical procedure to categorize a great number of fluorescent Pseudomonas strains by the range of siderophore production.