Iron Homeostasis and Environmental Responses in Cyanobacteria: Regulatory Networks Involving Fur

Abstract

Cyanobacteria are the only prokaryotes that perform oxygenic photosynthesis. Cyanobacteria populate an ample range of diverse and extreme habitats and contribute significantly to the global photosynthetic primary productivity and the fixation of atmospheric nitrogen. Some filamentous strains are capable of cell differentiation, which is unique among prokaryotes. Cyanobacteria also produce a source of interesting bioactive compounds as result of a rich secondary metabolism. However, massive proliferations of cyanobacteria in freshwater may produce cyanotoxins that, in critical levels, are toxic for eukaryotic organisms. All those processes rely on the adequate availability and management of iron, an essential nutrient for most forms of life. This chapter starts with an overview of the role of iron in the cyanobacterial metabolism and the adaptive responses of cyanobacteria to iron deficiency, one of the main stress factors in aquatic environments. Since Fur (ferric uptake regulator) is the master regulator of iron homeostasis in cyanobacteria, its central role in the cyanobacterial metabolism, including its potential functions as CXXC-based redox regulator and heme sensor, will be discussed.