The maintenance of iron homeostasis among prokaryotic phototrophs

Abstract

Like all prokaryotes, photosynthetic bacteria have had to solve the difficulty of acquiring poorly available iron in oxic environments and, at the same time, have had to manage the potential deleterious Fenton chemistry effects caused by this metal. In addition, photosynthesis requires a lot of iron for both the synthesis of the photosystem and the photosynthetic process itself. As a result of this iron need, phototrophs are good model organisms to study bacterial iron homeostasis. This review focuses on transcriptomic changes induced by iron limitation centering on major functional features of iron homeostasis such as the acquisition, storage, and regulation. We review evidence that iron limitation induces significant stress that triggers global transcriptional changes resulting in upregulation of iron import and storage while decreasing photosynthesis. Studies on transcription factors that regulate genes involved in iron homeostasis will also be covered, with the Ferric Uptake Regulator being the most understood. Finally, we will discuss the interference between iron and copper homeostasis, especially since iron transport systems make up a primary defense against copper poisoning.