AUTHOR=Domeignoz-Horta1 Luiz , Spor Aymé , Bru David , Breuil marie-christine , Bizouard Florian , Leonard Joel , PHILIPPOT Laurent 

TITLE=The diversity of the N2O reducers matters for the N2O:N2 denitrification end-product ratio across an annual and a perennial cropping system

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.00971

DOI=10.3389/fmicb.2015.00971

ISSN=1664-302X

ABSTRACT=<p>Agriculture is the main source of terrestrial emissions of N<sub>2</sub>O, a potent greenhouse gas and the main cause of ozone layer depletion. The reduction of N<sub>2</sub>O into N<sub>2</sub> by microorganisms carrying the nitrous oxide reductase gene (<italic>nosZ</italic>) is the only biological process known to eliminate this greenhouse gas. Recent studies showed that a previously unknown clade of N<sub>2</sub>O-reducers was related to the capacity of the soil to act as an N<sub>2</sub>O sink, opening the way for new strategies to mitigate emissions. Here, we investigated whether the agricultural practices could differently influence the two N<sub>2</sub>O reducer clades with consequences for denitrification end-products. The abundance of N<sub>2</sub>O-reducers and producers was quantified by real-time PCR, and the diversity of both <italic>nosZ</italic> clades was determined by 454 pyrosequencing. Potential N<sub>2</sub>O production and potential denitrification activity were used to calculate the denitrification gaseous end-product ratio. Overall, the results showed limited differences between management practices but there were significant differences between cropping systems in both the abundance and structure of the <italic>nosZII</italic> community, as well as in the [rN<sub>2</sub>O/r(N<sub>2</sub>O+N<sub>2</sub>)] ratio. More limited differences were observed in the <italic>nosZI</italic> community, suggesting that the newly identified <italic>nosZII</italic> clade is more sensitive than <italic>nosZI</italic> to environmental changes. Potential denitrification activity and potential N<sub>2</sub>O production were explained mainly by the soil properties while the diversity of the <italic>nosZII</italic> clade on its own explained 26% of the denitrification end-product ratio, which highlights the importance of understanding the ecology of this newly identified clade of N<sub>2</sub>O reducers for mitigation strategies.</p>