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| Titel |
Isotopologue signatures of nitrous oxide produced by nitrate-ammonifying bacteria isolated from soil |
| VerfasserIn |
Undine Behrendt, Reinhard Well, Anette Giesemann, Andreas Ulrich, Jürgen Augustin |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108269
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| Publikation (Nr.) |
 EGU/EGU2015-8017.pdf |
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| Zusammenfassung |
| Agricultural soils are the largest single source of anthropogenic N2O to the atmosphere,
primarily driven by microbiological processes such as denitrification and dissimilatory nitrate
reduction to ammonium (DNRA). Both processes occur under similar conditions of
low oxygen concentration and therefore, source partitioning of emitted N2O is
difficult. Understanding what controls the dynamics and reaction equilibrium of
denitrification and DNRA is important and may allow the development of more effective
mitigation strategies. 15N site preference (SP), i.e. the difference between 15N of
the central and peripheral N-position of the asymmetric N2O molecule, differs
depending on processes involved in N2O formation. Hence investigation of the
isotopomer ratios of formed N2O potentially presents a reliable mean to identify its
source.
In this study, bacterial isolates obtained from organic soils were screened for their ability
to reduce nitrate/nitrite to ammonium and to release N2O to the atmosphere. Taxonomic
characterisation of the strains revealed that N2O formation was only detected in ammonifying
strains affiliated to several genera of the family Enterobacteriaceae and strains belonging to
the genus Bacillus and Paenibacillus. Sampling of N2O was conducted by incubation of
strains under oxic and anoxic conditions. Investigation of the 15N site preference showed SP
values in the range of 39 to 57 ‰ . Incubation conditions had no influence on the SP. The
lowest values were achieved by a strain of the species Escherichia coli which was
included in this study as a DNRA reference bacterium harbouring the NrfA gene that is
coding the nitrite reductase, associated with respiratory nitrite ammonification. Soil
isolates showed SP-values higher than 40 ‰ . Comparison of these results with
SP-values of N2O produced by denitrifying bacteria in pure cultures (-5 to 0 ‰ )^[1,
2]revealedsignificantdifferences.Incontrast,N_2OproducedbydenitrifyingfungidisplayedSP -
valuesinarangeof21to36‰ [3] ,which are much closer to the values of N2O from the
investigated DNRA bacteria. However, the N2O formed under denitrifying conditions by
organisms investigated so far can be distinguished with respect to its source (DNRA or
denitrification) but a broader database is needed which cover a larger spectrum of
taxa.
[1] Sutka et al. Distinguishing nitrous oxide production from nitrification and
denitrification on the basis of isotopomer abundances. Appl. Env. Microbiol. 2006, 72,
638.
[2] Toyoda et al. Fractionation of N2O isotopomers during production by denitrifier. Soil
Biol. Biochem. 2005, 37, 1535.
[3] Rohe et al. Dual isotope and isotopomer signatures of nitrous oxide from fungal
denitrification – a pure culture study. Rapid Commun. Mass Spectrom. 2014, 28, 1893 |
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