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Dual isotope and isotopomer signatures of nitrous oxide from fungal denitrification – a pure culture study
Author(s) -
Rohe Lena,
Anderson TrauteHeidi,
Braker Gesche,
Flessa Heinz,
Giesemann Anette,
LewickaSzczebak Dominika,
WrageMönnig Nicole,
Well Reinhard
Publication year - 2014
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.6975
Subject(s) - denitrification , chemistry , denitrifying bacteria , environmental chemistry , nitrite , nitrous oxide , nitrate , electron acceptor , isotope fractionation , fractionation , nitrogen , organic chemistry
RATIONALE The contribution of fungal denitrification to the emission of the greenhouse gas nitrous oxide (N 2 O) from soil has not yet been sufficiently investigated. The intramolecular 15 N site preference (SP) of N 2 O could provide a tool to distinguish between N 2 O produced by bacteria or fungi, since in previous studies fungi exhibited much higher SP values than bacteria. METHODS To further constrain isotopic evidence of fungal denitrification, we incubated six soil fungal strains under denitrifying conditions, with either NO 3 − or NO 2 − as the electron acceptor, and measured the isotopic signature (δ 18 O, δ 15 N bulk and SP values) of the N 2 O produced. The nitrogen isotopic fractionation was calculated and the oxygen isotope exchange associated with particular fungal enzymes was estimated. RESULTS Five fungi of the order Hypocreales produced N 2 O with a SP of 35.1 ± 1.7 ‰ after 7 days of anaerobic incubation independent of the electron acceptor, whereas one Sordariales species produced N 2 O from NO 2 − only, with a SP value of 21.9 ± 1.4 ‰. Smaller isotope effects of 15 N bulk were associated with larger N 2 O production. The δ 18 O values were influenced by oxygen exchange between water and denitrification intermediates, which occurred primarily at the nitrite reduction step. CONCLUSIONS Our results confirm that SP of N 2 O is a promising tool to differentiate between fungal and bacterial N 2 O from denitrification. Modelling of oxygen isotope fractionation processes indicated that the contribution of the NO 2 − 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 18 O values of the N 2 O produced. Copyright © 2014 John Wiley & Sons, Ltd.