P. aeruginosa is an ESKAPE pathogen of special concern due to its resistance to many antibiotics. Currently, the options for treatment of P. aeruginosa infections are limited, especially in immunocompromised patients. Bacterial proliferation depends on acquisition of metal ions, in particular iron and zinc, which serve as co-factors in many vitally important enzymes. Bacterial siderophores are secondary metabolites secreted by bacteria, which chelate metal ions and are taken up using specific transport mechanisms (Shalk, 2022). Targeting the re-uptake process of the of ion-loaded siderophores can provide an alternative strategy for P. aeruginosa treatment. Iron ions are transported with the help of pyoverdine and pyochelin (Hartney, 2013), while zinc ions are taken up using pseudopaline (Ghssein, 2022).

3D structures of the outer membrane transporters for siderophores, FpvA, FptA and CntO, in complex with their cognate substrates are available. A target-based approach will comprise in silico docking of a collection of known bacterial siderophore structures to these transporters with the aim of potentially identifying those which could bind but may block the transport itself. An alternative strategy will be computer-assisted modeling aimed at “minimization” of the pseudomonal siderophore structures, which would render them able to bind to transporters while unable to bind metal ions. Such “minimized” siderophores (Msids) could serve as competitive inhibitors of the metal ion re-uptake. Selected Msids will be synthesized or genetically engineered (if they are biosynthesized via non-ribosomal peptide synthetase pathways) and tested for the ability to inhibit P. aeruginosa growth in the conditions of limited and unlimited access to metal ions. A phenotype-based approach will focus on the discovery of new bacterial siderophores that may act as competitive inhibitors of metal ion uptake in P. aeruginosa. The aim is to discover siderophores that bind to the FpvA, FptA or CntO, but are not transported inside the cell.  A subset of actinomycete bacteria collection with sequenced genomes will be mined for the siderophore biosynthesis gene clusters (BGCs). BGCs potentially encoding new siderophores will be heterologously expressed in genetically engineered bacterial hosts or their expression activated in the original host, followed by isolation and structural characterization. Docking studies will then be performed, aiming at selection of candidates for biological testing.