Alternative nitrogenase activity in the environment and nitrogen cycle implications

Xinning Zhang, Darcy L. McRose, Romain Darnajoux, J. P. Bellenger, Francois M. M. Morel, Anne M.L. Kraepiel

Research output: Contribution to journalLetterpeer-review

46 Scopus citations


Biological nitrogen fixation, the main natural input of fixed nitrogen into the biosphere, is catalyzed by Mo-, V-, or Fe-only nitrogenase metalloenzymes. Although “alternative” V- and Fe-only nitrogenase genes are found in many environments, the contribution of these isoenzymes to N2 fixation is unknown. Here we present a new method (ISARA, isotopic acetylene reduction assay) that distinguishes canonical Mo and alternative nitrogenase activities based on in vivo 13C fractionation of acetylene reduction to ethylene (13εMo = 13.1–14.7 ‰, 13εV = 7.5–8.8 ‰, 13εFe = 5.8–6.5 ‰). ISARA analyses indicate significant contributions of alternative nitrogen fixation in boreal cyanolichens and salt marshes (~10–40 % acetylene reduction, ~20–55 % N2 fixed). These results affect the quantitative interpretation of natural abundance 15N data or traditional acetylene reduction assays. They also invite a reexamination of the conditions under which the different nitrogenase isozymes are active and suggest significant interactions between the cycles of nitrogen and trace metals.

Original languageEnglish (US)
Pages (from-to)189-198
Number of pages10
Issue number2-3
StatePublished - Feb 1 2016

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Water Science and Technology
  • Earth-Surface Processes


  • Alternative nitrogenase
  • Nitrogen cycle
  • Nitrogen fixation
  • Stable isotopes
  • Trace metals


Dive into the research topics of 'Alternative nitrogenase activity in the environment and nitrogen cycle implications'. Together they form a unique fingerprint.

Cite this