Bacterial Siderophore Production in Metal-Rich Environments: Underexplored Sources of Siderophores and Insights into Bioremediation

Siderophores are iron-chelating secondary metabolites that increase the bioavailability of the essential nutrient iron. These molecules have several diverse applications in agriculture, pharmaceuticals, and bioremediation. Their diverse and inherent properties have made them ideal targets for natural product characterization using culture-dependent and culture-independent methods that often combine cell cultivation with genomic analyses. However, despite decades of work characterizing these molecules, there is a dearth of information concerning siderophore biosynthesis in metal-rich environments, such as acid mine drainage sites, volcanic ash, and other sources of metal pollution that are not deficient in iron. This Review focuses on bacterial siderophore biosynthesis, regulation, and transport as well as the roles of these metabolites within metal-rich environments. The effects of noniron metals on siderophore production are discussed in addition to the methods and challenges used to investigate and leverage siderophore biosynthesis for sustainable environmental and agricultural practices. The examples discussed underscore the need for metal-rich environments to be further explored for the identification of novel siderophores and siderophore-producing organisms that can be exploited for human use.