Chapter 7 - Iron homeostasis of cyanobacteria: advancements in siderophores and metal transporters

Abstract

Due to their photoautotrophic metabolism, cyanobacteria have a significantly higher demand on metals when compared to microorganisms with chemoheterotrophic and even photoheterotrophic life style. At the same time, cyanobacteria are found in most habitats on the Earth and thus are exposed to very variable environmental conditions with respect to metal availability. This enforced the evolution of multiple mechanisms for metal uptake under limiting conditions as well as to prevent envenoming under exposure to high concentrations of a certain metal. Within this article, we will discuss the different siderophores identified from cyanobacteria as well as the current understanding of their synthesis and secretion. Moreover, we discuss the different modes of uptake and the transporter involved, as well as our current advancements of the regulation of these systems. While most of the discussion will be centered around the uptake of iron, we will summarize the information for the cycles of other metals as well.