The production of siderophore analogues using precursor-directed biosynthesis

Siderophores are low-molecular-weight organic bacterial and fungal secondary metabolites that form high affinity complexes with Fe(III). These Fe(III)-siderophore complexes are part of the siderophore-mediated Fe(III) uptake mechanism, which is the most widespread strategy used by microbes to access sufficient iron for growth. Microbial competition for limited iron is met by biosynthetic gene clusters that encode for the biosynthesis of siderophores with variable molecular scaffolds and iron binding motifs. Some classes of siderophores have well understood biosynthetic pathways, which opens opportunities to further expand structural and property diversity using precursor-directed biosynthesis (PDB). PDB involves augmenting culture medium with non-native substrates to compete against native substrates during metabolite assembly. This chapter provides background information and technical details of conducting a PDB experiment towards producing a range of different analogues of the archetypal hydroxamic acid siderophore desferrioxamine B. This includes processes to semi-purify the culture supernatant and the use of liquid chromatography-tandem mass spectrometry for downstream analysis of analogues and groups of constitutional isomers.