Iron is the fourth most abundant element on Earth and is essential for almost all living organisms. However, it is not accessible to cells in every environment. Ferric iron solubility is low at physiological pH, and in aerobic environments, ferrous iron is highly toxic. Thus, iron is not free but bound to proteins [Clarke et al., 2001; Taylor and Kelly, 2010]. In complex organisms, the majority of iron is intracellularly sequestered within heme-compounds or iron-containing proteins or is stored in ferritin.