NUTRIENT UPTAKE INTERACTIONS: SIDEROPHORE PRODUCTION AND NITROGEN FIXATION IN ANABAENA CULTURE EXPERIMENTS

Siderophore production and nitrogen fixation are two energetically costly processes used by microorganisms to cope with low availability of the necessary elements iron and nitrogen. There is a paradoxical relationship between the two processes. Siderophores can make iron available for nitrogen fixation but they are rich in nitrogen. We know that nitrogen fixation occurs under low levels of available nitrogen and high levels of available iron while siderophore production occurs at high levels of nitrogen and low levels of available iron. This relationship has led other investigators to hypothesize that the two processes cannot occur simultaneously. Still, colimitation by iron and nitrogen is a common problem faced by microbes, which implies that adaptations have been made to survive under these conditions. This study aims to discover threshold levels of iron and nitrogen where these processes can both take place. Anabaena sp. will be cultured with various concentrations of iron to determine the highest concentration where siderophore production can occur. Additionally, Anabaena sp. will be cultured with various nitrogen concentrations to determine the highest concentration where nitrogen fixation can occur. We expect that a culture experiment with these threshold levels will provide an environment where siderophore production and nitrogen fixation will occur simultaneously. This study has important implications for discovering the mechanisms behind fundamental biological processes in aquatic species; learning about siderophores and nitrogen fixation will provide insight into the adaptations that aquatic species have made to their environments. This knowledge can be applied towards reconstructing histories of past environmental conditions based on paleolimnological records.