Dual isotope and isotopomer signatures of nitrous oxide from fungal denitrification – a pure culture study. (15th September 2014)

• Record Type: Journal Article
• Authors: Rohe, Lena; Anderson, Traute‐Heidi; Braker, Gesche; Flessa, Heinz; Giesemann, Anette; Lewicka‐Szczebak, Dominika; Wrage‐Mönnig, Nicole; Well, Reinhard
• Is Part Of: Rapid communications in mass spectrometry. Volume 28:Number 17(2014)
• Page Start: 1893
• Page End: 1903
• Publication Date: 2014-09-15
• Subjects: Mass spectrometry -- Periodicals; 543.65
• DOI: 10.1002/rcm.6975
• Languages: English
• ISSNs: 0951-4198

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="rcm6975-sec-0001" sec-type="section"> <title>RATIONALE</title> <p>The contribution of fungal denitrification to the emission of the greenhouse gas nitrous oxide (N<sub>2</sub>O) from soil has not yet been sufficiently investigated. The intramolecular <sup>15</sup>N site preference (SP) of N<sub>2</sub>O could provide a tool to distinguish between N<sub>2</sub>O produced by bacteria or fungi, since in previous studies fungi exhibited much higher SP values than bacteria.</p> </sec> <sec id="rcm6975-sec-0002" sec-type="section"> <title>METHODS</title> <p>To further constrain isotopic evidence of fungal denitrification, we incubated six soil fungal strains under denitrifying conditions, with either NO<sub>3</sub><sup>−</sup> or NO<sub>2</sub><sup>−</sup> as the electron acceptor, and measured the isotopic signature (δ<sup>18</sup>O, δ<sup>15</sup>N<sub>bulk</sub> and SP values) of the N<sub>2</sub>O produced. The nitrogen isotopic fractionation was calculated and the oxygen isotope exchange associated with particular fungal enzymes was estimated.</p> </sec> <sec id="rcm6975-sec-0003" sec-type="section"> <title>RESULTS</title> <p>Five fungi of the order <italic>Hypocreales</italic> produced N<sub>2</sub>O with a SP of 35.1 ± 1.7 ‰ after 7 days of anaerobic incubation independent of the electron acceptor, whereas one <italic>Sordariales</italic> species produced N<sub>2</sub>O from NO<sub>2</sub><sup>−</sup> only, with a SP value of 21.9 ± 1.4 ‰. Smaller isotope effects of <sup>15</sup>N<sub>bulk</sub> were associated with larger N<sub>2</sub>O production. The δ<sup>18</sup>O values were influenced by oxygen exchange between water and denitrification intermediates, which occurred primarily at the nitrite reduction step.</p> </sec> <sec id="rcm6975-sec-0004" sec-type="section"> <title>CONCLUSIONS</title> <p>Our results confirm that SP of N<sub>2</sub>O is a promising tool to differentiate between fungal and bacterial N<sub>2</sub>O from denitrification. Modelling of oxygen isotope fractionation processes indicated that the contribution of the NO<sub>2</sub><sup>−</sup> and NO reduction steps to the total oxygen exchange differed among the various fungal species studied. However, more information is needed about different biological orders of fungi as they may differ in denitrification enzymes and consequently in the SP and δ<sup>18</sup>O values of the N<sub>2</sub>O produced. Copyright © 2014 John Wiley & Sons, Ltd.</p> </sec> </abstract>