Atmospheric nitrogen fixation by eukaryotes: Should we reconsider the nitrogen cycle in nature?

Abstract

Nitrogen is the most abundant element in our planets atmosphere. Approximately 78% of the atmosphere is made up of nitrogen gas (N2). It is essential for organisms, as a major component of biomolecules and cellular biochemistry. Until today, atmospheric N2 assimilation in eukaryotic organisms has been reported to occur only through specific symbiotic N2-fixing bacterial groups that make it available to plants, the base of the food chain. In this work, using Gas Chromatography with Thermal Conductivity Detection, we proved the direct consumption of atmospheric N2 by eukaryotic organisms. Three yeast species: Debaryomyces hansenii, Metschnikowia reukaufii and model-species Saccharomyces cerevisiae are able to directly assimilate atmospheric nitrogen in various conditions, with a yet unknown mechanisms that are not based on the presence of known N2-fixation enzymes. Our findings could change the way we consider the N2-assimilation in nature, laying the basis for future focused studies on the molecular mechanism underling the biological phenomenon of eukaryotic N2-assimilation.