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Use of oxygen isotopes to differentiate between nitrous oxide produced by fungi or bacteria during denitrification
Author(s) -
Rohe Lena,
Well Reinhard,
LewickaSzczebak Dominika
Publication year - 2017
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.7909
Subject(s) - denitrifying bacteria , chemistry , fractionation , denitrification , environmental chemistry , isotope fractionation , bacteria , isotopic signature , oxygen isotope ratio cycle , isotopes of nitrogen , isotope analysis , mass independent fractionation , isotope , nitrogen , chromatography , ecology , biology , organic chemistry , physics , quantum mechanics , genetics
Rationale Fungal denitrifiers can contribute substantially to N 2 O emissions from arable soil and show a distinct site preference for N 2 O (SP(N 2 O)). This study sought to identify another process‐specific isotopic tool to improve precise identification of N 2 O of fungal origin by mass spectrometric analysis of the N 2 O produced. Methods Three pure bacterial and three fungal species were incubated under denitrifying conditions in treatments with natural abundance and stable isotope labelling to analyse the N 2 O produced. Combining different applications of isotope ratio mass spectrometry enabled us to estimate the oxygen (O) exchange accelerated by denitrifying enzymes and the ongoing microbial pathway in parallel. This experimental set‐up allowed the determination of δ 18 O(N 2 O) values and isotopic fractionation of O, as well as SP(N 2 O) values, as a perspective to differentiate between microbial denitrifiers. Results Oxygen exchange during N 2 O production was lower for bacteria than for fungi, differed between species, and depended also on incubation time. Apparent O isotopic fractionation during denitrification was in a similar range for bacteria and fungi, but application of the fractionation model indicated that different enzymes in bacteria and fungi were responsible for O exchange. This difference was associated with different isotopic fractionation for bacteria and fungi. Conclusions δ 18 O(N 2 O) values depend on isotopic fractionation and isotopic fractionation may differ between processes and organism groups. By comparing SP(N 2 O) values, O exchange and the isotopic signature of precursors, we propose here a novel tool for differentiating between different sources of N 2 O.