Nos tutelles

CNRS Ecole Centrale de Lyon Université de Lyon Université Lyon 1 INSA de Lyon

Nos partenaires



Accueil > Thèses et HDR > Thèses en 2016

06/12/216 - Christoph KEUSCHNIG

publié le , mis à jour le


Ajouter un événement iCal

Christoph KEUCHNIG soutient sa thèse le 06/12/2016 - 10h - Amphi 201 - ECL

Titre :
Fungal and bacterial involvement in nitrogen cycling and N2O production in soil

Jury :

  • Directeurs de thèse : SIMONET Pascal ; LAROSE Catherine
  • Rapporteurs  : DE BOER Wietse ; HOFMOCKEL Kirsten
  • Examinateurs : ZECHMEISTER-BOLTENSTERN Sophie ; KLEMEDTSSON Leif ; VOGEL Timothy ; SIME-NGANDO Télesphore

Résumé :
The main objective of this thesis is to determine the role of microbial communities in N2O emissions from soil, and more specifically to define to what extent fungi are involved. Therefore, their community structure at the micro scale, their behavior in reducing nitrogen and producing N2O, and their impact on nitrogen cycling communities as decomposers in soil were investigated. Analysis of soil fractions of unmanaged, pristine Rothamsted Park Grass soil showed that fungal communities change within isolated fractions in contrast to bacterial communities. Also, nitrifying, denitrifying and N2O reducing potentials were detected in all fractions and found to be linked to carbon and nitrogen chemistry. Pure culture experiments on 24 fungal strains quantifying NO and N2O production from nitrite showed that Fusarium species are true N2O producers among fungi. Monitoring NO revealed that nitrite medium is unstable under anoxic conditions and produces NO abiotically, which implies that low N2O producing strains are actually detoxifying this NO rather than respiring it, as previously assumed. The lack of a nirK - p450nor in most fungi supported this hypothesis. Interspecies relationships between fungi and bacteria were studied following community development after organic matter addition. Different organic amendments triggered distinct responses of a soil community with respect to bacterial and fungal activity. Functional signatures identified in this study corroborated our hypothesis that fungi are involved in N2O production by influencing a N-cycling bacterial community via carbohydrate degradation processes. The results from this thesis provide a basis for exploring interspecies relationships in nitrogen cycling processes in soil and mark a step towards integrating all members of the community in soil ecosystem research.

Voir en ligne : texte complet