Abstract
Among 50 strains of Pseudomonas aeruginosa tested for the resistance to antibiotics, strain ryn32 was selected for this study based on its resistance level. It showed complete resistance toward aztreonam and almost complete resistance (96%) against kanamycin. Iron nanoparticles (FeNPs) were then prepared and found with diameters 30-50 nm. The threshold level of FeNPs for pyoverdines (PVDs) production by P. aeruginosa ryn32 was found at 25 μM concentration. PVDs production was optimal with pH 7.5, 35°C, succinate as carbon source, ammonium sulfate as nitrogen source at 60 hr fermentation time. Interestingly, when used the PVDs as conjugates with FeNPs they showed antibacterial action against the producing strain and some other gram-negative bacteria. This suggests that the conjugates enter the bacterial cell via the ferriPVDs uptake pathway, which triggers the accumulation of FeNPs inside the cell, which is crucial on bacterial viability. Growth stimulation with the same concentrations of FeNPs and PVDs in separate treatments supported this view.