title: Chemical formation of hybrid di-nitrogen calls fungal codenitrification into question.
abstract: Removal of excess nitrogen (N) can best be achieved through denitrification processes that transform N in water and terrestrial ecosystems to di-nitrogen (N2) gas. The greenhouse gas nitrous oxide (N2O) is considered an intermediate or end-product in denitrification pathways. Both abiotic and biotic denitrification processes use a single N source to form N2O. However, N2can be formed from two distinct N sources (known as hybrid N2) through biologically mediated processes of anammox and codenitrification. We questioned if hybrid N2produced during fungal incubation at neutral pH could be attributed to abiotic nitrosation and if N2O was consumed during N2formation. Experiments with gas chromatography indicated N2was formed in the presence of live and dead fungi and in the absence of fungi, while N2O steadily increased. We used isotope pairing techniques and confirmed abiotic production of hybrid N2under both anoxic and 20% O2atmosphere conditions. Our findings question the assumptions that (1) N2O is an intermediate required for N2formation, (2) production of N2and N2O requires anaerobiosis, and (3) hybrid N2is evidence of codenitrification and/or anammox. The N cycle framework should include abiotic production of N2.
authors.affiliation: Landcare Research, Gerald Street, Lincoln, New Zealand.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Phillips
authors.affiliation: Dept. of Biological Sciences, Virginia Institute of Marine Science, Gloucester Point, Virginia, USA.
authors.forename: Bongkeun
authors.initials: B
authors.lastname: Song
authors.affiliation: Landcare Research, Gerald Street, Lincoln, New Zealand.
authors.forename: Andrew M S
authors.initials: AM
authors.lastname: McMillan
authors.affiliation: Landcare Research, Gerald Street, Lincoln, New Zealand.
authors.forename: Gwen
authors.initials: G
authors.lastname: Grelet
authors.affiliation: Landcare Research, Gerald Street, Lincoln, New Zealand.
authors.forename: Bevan S
authors.initials: BS
authors.lastname: Weir
authors.affiliation: Landcare Research, Gerald Street, Lincoln, New Zealand.
authors.forename: Thilak
authors.initials: T
authors.lastname: Palmada
authors.affiliation: Dept. of Marine Sciences, University of Connecticut, Groton, Connecticut, USA.
authors.forename: Craig
authors.initials: C
authors.lastname: Tobias
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D002849:Chromatography, Gas; D058440:Denitrification; D005658:Fungi / Q000378:metabolism*; D000074382:Greenhouse Gases / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D009609:Nitrous Oxide / Q000032:analysis*
chemical_list: D000074382:Greenhouse Gases; D009609:Nitrous Oxide; D009584:Nitrogen