Prokaryotic Ferrous Iron Transport: Exploiting Pools of Reduced Iron Across Multiple Microbial Environments

Iron is essential to nearly all forms of life, but the redox activity of this element necessitates its cellular regulation. All iron-utilizing organisms require this nutrient to be tightly managed, which is accomplished by a suite of proteins and nucleic acids involved in the acquisition, the delivery, the storage, the regulation, and the export of this essential element. For infectious organisms, iron acquisition systems are commonly associated with intracellular growth, survival, and virulence of pathogens, which are dynamically able to modify their iron uptake strategies in response to changing host environments. The past few decades have been marked with an increased understanding of pathogenic ferric iron (Fe3+) and heme acquisition. In contrast, though the necessity of ferrous iron (Fe2+) transport for pathogenesis has been established, the precise details of this process remain enigmatic, and Fe2+ transporters remain unexploited as drug targets to combat drug-resistant organisms. This chapter will overview a current understanding of Fe2+ transport in microbes and highlight gaps in our knowledge that must be closed in order to establish a comprehensive understanding of unicellular Fe2+ metabolism.