Inhibition of nitrogenase by oxygen in marine cyanobacteria controls the global nitrogen and oxygen cycles

I. Berman-Frank (1, 2) , Y.-B. Chen (1) , Y. Gerchman (3) , G. C. Dismukes (3) , P. G. Falkowski (1, 4)

1 Institute of Marine and Coastal Science
2 Faculty of Life Sciences
3 PEI - Princeton Environmental Institute [Princeton University]
4 Department of Geological Sciences

Cyanobacterial N₂-fixation supplies the vast majority of biologically accessible inorganic nitrogen to nutrient-poor aquatic ecosystems. The process, catalyzed by the heterodimeric protein complex, nitrogenase, is thought to predate that of oxygenic photosynthesis. Remarkably, while the enzyme plays such a critical role in Earth's biogeochemical cycles, the activity of nitrogenase in cyanobacteria is markedly inhibited in vivo at a post-translational level by the concentration of O₂ in the contemporary atmosphere leading to metabolic and biogeochemical inefficiency in N₂ fixation. We illustrate this crippling effect with data from Trichodesmium spp. an important contributor of "new nitrogen" to the world's subtropical and tropical oceans. The enzymatic inefficiency of nitrogenase imposes a major elemental taxation on diazotrophic cyanobacteria both in the costs of protein synthesis and for scarce trace elements, such as iron. This restriction has, in turn, led to a global limitation of fixed nitrogen in the contemporary oceans and provides a strong biological control on the upper bound of oxygen concentration in Earth's atmosphere.

Domaines: Cosmologie et astrophysique extra-galactique [astro-ph.CO]; Astrophysique [astro-ph]; Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

I. Berman-Frank, Y.-B. Chen, Y. Gerchman, G. C. Dismukes, P. G. Falkowski. Inhibition of nitrogenase by oxygen in marine cyanobacteria controls the global nitrogen and oxygen cycles. Biogeosciences Discussions, 2005, 2 (2), pp.261-273. ⟨hal-00297738⟩