H2O2 Tolerance in Pseudomonas Fluorescens: Synergy between Pyoverdine-Iron(III) Complex and a Blue Extracellular Product Revealed by a Nanotechnology-Based Electrochemical Approach

Some strains of Pseudomonas fluorescens generate a blue extracellular product conferring high resistance to oxidative stress with respect to white mutants. As conventional methods fail to discriminate among blue and white microorganisms, the mechanism of H2O2 scavenging activity of colored P. fluorescens was here investigated by an electrochemical approach coupled to nanotechnology. Hydrophilic pyoverdine, the most represented siderophore, was studied as possible electrocatalytic partner of the hydrophobic blue bacterial extract. Peculiar iron oxide nanoparticles were used as a support for the siderophore immobilization, mimicking a water soluble FeIII‐siderophore complex. Interestingly, even if these two counterparts are not redox active when used alone, the siderophore was able to trigger the crude colored bacterial extract into a selective catalyst for hydrogen peroxide elimination. The present study, besides shedding light into the bacterial mechanisms behind the tolerance to H2O2, highlights the advantages of using nanotechnology as complement of classical electrochemical methods aimed at addressing complex biological issues.