Iron Homeostasis in Azotobacter vinelandii

SIMPLE SUMMARY: Azotobacter vinelandii is a model organism used to study biological nitrogen fixation, a process by which nitrogen gas is transformed into ammonia, a form of nitrogen that can be assimilated by most organisms. This requires the synthesis and transfer of specific iron-containing cofactors to enzymes involved in nitrogen fixation. There are large gaps in our knowledge of iron uptake and utilization by A. vinelandii. In this review, our goal is to summarize current knowledge, propose novel elements based on our current understanding of bacterial iron homeostasis, and highlight those areas requiring more detailed research. ABSTRACT: Iron is an essential nutrient for all life forms. Specialized mechanisms exist in bacteria to ensure iron uptake and its delivery to key enzymes within the cell, while preventing toxicity. Iron uptake and exchange networks must adapt to the different environmental conditions, particularly those that require the biosynthesis of multiple iron proteins, such as nitrogen fixation. In this review, we outline the mechanisms that the model diazotrophic bacterium Azotobacter vinelandii uses to ensure iron nutrition and how it adapts Fe metabolism to diazotrophic growth.