Diurnally dynamic iron allocation promotes N2 fixation in marine dominant diazotroph Trichodesmium

Trichodesmium is the dominant photoautotrophic dinitrogen (N2) fixer (diazotroph) in ocean. Iron an important factor limiting growth of marine diazotrophs including mainly because high iron content its N2-fixing enzyme, nitrogenase. However, it still lacks a quantitative understanding how dynamic allocation among physiological processes acts to regulate and N2 fixation Trichodesmium. Here, we constructed model trichome which intracellular could be dynamically re-allocated photosystems nitrogenase during daytime. The results demonstrate that enhances modeled rates Trichodesmium, especially iron-limited conditions, albeit having marginal impact under concentrations. Although reuse day apparent cause can benefit limitation, our reveals two mechanisms. First, release from downregulates oxygen (O2) production reduces demand respiratory protection, process wastefully respires carbohydrates create lower O2 window for fixation. Hence, more used growth. Second, early daytime, period when photosynthesis active high, amount trapped inactivated induced by O2. This mechanism further increases use efficiency Overall, study provides mechanistic insight into diurnal alleviate limitation