EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Gas kinetics and stoichiometry from four fungi incubated under conditions favouring denitrification

Lena Rohe1, Reinhard Well1, Shahid Nadeem2, and Peter Dörsch2
Lena Rohe et al.
  • 1Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany (
  • 2Norwegian University of Life Sciences (NMBU), Department of Environmental Sciences (IMV), Ås, Norway

Even though the ability of fungi to produce the greenhouse gas nitrous oxide (N2O) during denitrification has been demonstrated, the proportion N2O emissions from fungal denitrification in soils cannot yet be determined or predicted. In order to develop methods for estimating the fungal proportion, N2O must be partitioned to bacterial and fungal denitrification. The denitrification regulatory phenotype (DRP) is well described for a number of bacterial strains (Bergaust et al. 2010, Bergaust et al. 2011), but to our knowledge there are only few data relating to the fungal DRP in terms of oxygen (O2) tension in fully stirred cultures at which they start producing N2O. The aim of this study was to analyse the kinetics of fungal denitrification combined with analysis of the isotopic composition of N2O. In particular, the 15N site preference of N2O (SP-N2O) is known to be a promising tool to differentiate between N2O produced during bacterial and fungal denitrification.

Four fungal species (Fusarium oxysporum, Fusarium decemcellulare, Fusarium solani fsp. pisi and Chaetomium funicola) were incubated as batch cultures in a robotized incubation system (Molstad et al. 2007) for 165h. Batch cultures were incubated in 120 ml flasks containing 50 ml of growth medium amended with ample amounts of carbon and nitrate in a He atmosphere with 2 vol%O2. To test for pH effects, a complex medium (Shoun et al. 1992) with pH values adjusted to 6.9 and 7.4 as well a minimal medium (Dox 1910) with a pH value of about 7.9 were used. O2 consumption and production of nitric oxide (NO), N2O, dinitrogen (N2) and carbon dioxide (CO2) were monitored at high temporal resolution while isotopic composition of N2O was analysed in samples taken manually at selected time points.

All four fungal cultures quickly consumed O2. NO production increased strongly before O2 was completely consumed and was followed by immediate N2O production. The kinetics of N2O production differed to published kinetics of denitrifying prokaryotes by showing a lower sensitivity to O2. This could result in a larger share of fungal denitrification under microaerobic conditions in soil.

Isotopic analysis of N2O confirmed previous results of specifically high SP-N2O values of fungal produced N2O. We further showed that SP-N2O values of fungal N2O are quite stable and do not depend on denitrification kinetics. Likewise, incubation conditions such as pH of the medium had little impact on SP-N2O values. These findings support the usage of SP-N2O values for partitioning N2O soil fluxes and provide a tool to study the biology of fungal denitrification under field conditions, which is needed to develop mitigation strategies of N2O from fungal denitrification.


  • Bergaust, Y. Mao, L. R. Bakken, Å. Frostegård, Appl Environ Microbiol 2010, 76.
  • Bergaust, L. R. Bakken, Å. Frostegård, Biochem Soc Trans 2011, 39.
  • Molstad, P. Dörsch, L. R. Bakken, J Microbiol Methods 2007, 71, 202.
  • Shoun, D.-H. Kim, H. Uchiyama, J. Sugiyama, FEMS Microbiol. Lett. 1992, 94, 277.
  • W. Dox, U.S. Dept. of Agriculture, Bureau of Animal Industry, Washington, D.C., 1910, 70 p.

How to cite: Rohe, L., Well, R., Nadeem, S., and Dörsch, P.: Gas kinetics and stoichiometry from four fungi incubated under conditions favouring denitrification, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5064,, 2022.