Nitrogen and oxygen isotope fractionation during dissimilatory nitrate reduction by denitrifying bacteria

Granger, Julie; Sigman, Daniel M.; Lehmann, Moritz F.; Tortell, Philippe D.

doi:10.4319/lo.2008.53.6.2533

Cited by 391 publications

(519 citation statements)

References 54 publications

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“…This was particularly apparent for CN25 and CN75 enrichments grown at low [NH 4 þ ] (o20 mM), which exhibited a considerable lag phase before the commencement of ammonia oxidation. Variable e values have been observed in many other organisms, including denitrifiers (Granger et al, 2008), methane oxidizers (Templeton et al, 2006), sulfate reducers (Habicht et al, 2005) and nitrite oxidizers (Casciotti, 2009;Buchwald and Casciotti, 2010), and during assimilation of NH 4 þ by heterotrophic bacteria (Hoch et al, 1992) but has not previously been reported in ammonia-oxidizing organisms. We explore two hypotheses that could explain a large apparent isotope effect at the early stages of growth (Figure 6).…”

Section: Nitrogen Isotopic Fractionationmentioning

confidence: 99%

Enrichment and characterization of ammonia-oxidizing archaea from the open ocean: phylogeny, physiology and stable isotope fractionation

2011

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Archaeal genes for ammonia oxidation are widespread in the marine environment, but direct physiological evidence for ammonia oxidation by marine archaea is limited. We report the enrichment and characterization of three strains of pelagic ammonia-oxidizing archaea (AOA) from the North Pacific Ocean that have been maintained in laboratory culture for over 3 years. Phylogenetic analyses indicate the three strains belong to a previously identified clade of water column-associated AOA and possess 16S ribosomal RNA genes and ammonia monooxygenase subunit a (amoA) genes highly similar (98-99% identity) to those recovered in DNA and complementary DNA clone libraries from the open ocean. The strains grow in natural seawaterbased liquid medium while stoichiometrically converting ammonia (NH 3 ) to nitrite (NO 2 À ). Ammonia oxidation by the enrichments is only partially inhibited by allylthiourea at concentrations known to completely inhibit cultivated ammonia-oxidizing bacteria. The three strains were used to determine the nitrogen stable isotope effect ( 15 e NH3 ) during archaeal ammonia oxidation, an important parameter for interpreting stable isotope ratios in the environment. Archaeal 15 e NH3 ranged from 13% to 41%, within the range of that previously reported for ammonia-oxidizing bacteria. Despite low amino acid identity between the archaeal and bacterial Amo proteins, their functional diversity as captured by 15 e NH3 is similar.

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Section: Nitrogen Isotopic Fractionationmentioning

confidence: 99%

Enrichment and characterization of ammonia-oxidizing archaea from the open ocean: phylogeny, physiology and stable isotope fractionation

2011

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“…Dissimilatory NO − 3 reduction to NO − 2 is known to produce N and O isotopic fractionation with a characteristic slope near 1 (Granger et al, 2008). Deviations from this relationship are a common feature of the limited data sets available for OMZ's and have been interpreted as evidence for co-occurrence of other N-transformation processes including NO − 2 oxidation and contributions from N 2 fixation (Casciotti and McIlvin, 2007;Sigman et al, 2005).…”

Section: An N-loss Hotspotmentioning

confidence: 99%

“…Dissimilatory NO − 3 reduction to NO − 2 is known to produce both strong N as well as O isotopic fractionation (Granger et al, 2008) (Casciotti and McIlvin, 2007; fractionation factor, ε ∼ 25 ‰). Presumably because 15 N-depleted N 2 gas is ultimately produced via preferential loss of 14 N, this process is responsible for enriching the oceanic fixed-N inventory in 15 N (δ 15 N ∼ 5 ‰ relative to atmospheric N 2 ; Sigman et al, 2009) as compared to sources (e.g.…”

Section: A Altabet Et Al: An Eddy-stimulated Hotspot For Fixed Nmentioning

confidence: 99%

An eddy-stimulated hotspot for fixed nitrogen-loss from the Peru oxygen minimum zone

et al. 2012

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Abstract. Fixed nitrogen (N) loss to biogenic N 2 in intense oceanic O 2 minimum zones (OMZ) accounts for a large fraction of the global N sink and is an essential control on the ocean's N-budget. However, major uncertainties exist regarding microbial pathways as well as net impact on the magnitude of N-loss and the ocean's overall N-budget. Here we report the discovery of a N-loss hotspot in the Peru OMZ associated with a coastally trapped mesoscale eddy that is marked by an extreme N-deficit matched by biogenic N 2 production, high NO − 2 levels, and the highest isotope enrichments observed so far in OMZ's for the residual NO − 3 . High sea surface chlorophyll in seaward flowing streamers provides evidence for offshore eddy transport of highly productive, inshore water. Resulting pulses in the downward flux of particles likely stimulated heterotrophic dissimilatory NO − 3 reduction and subsequent production of biogenic N 2 within the OMZ. A shallower biogenic N 2 maximum within the oxycline is likely a feature advected by the eddy streamer from the shelf. Eddy-associated temporal-spatial heterogeneity of N-loss, mediated by a local succession of microbial processes, may explain inconsistencies observed among prior studies. Similar transient enhancements of N-loss likely occur within all other major OMZ's exerting a major influence on global ocean N and N isotope budgets.

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“…3B) and serves as a diagnostic of denitrification (14,(20)(21)(22). This regression of δ 18 O NO3 versus δ 15 N NO3 excluded one sample (Well JD05, 12 July) that had a lighter isotopic composition and higher NO 3 − concentration than the others (Fig.…”

Section: Significancementioning

confidence: 99%

“…− is not replenished or consumed by other processes, denitrification progressively enriches both 18 O and 15 N in the residual NO 3 − , with an O:N fractionation ratio of 0.4-0.7 in the field (14,20,21) and up to 1.0 in laboratory studies (22 Table S1), including the HBEF (10,17), have revealed little if any isotopic evidence of denitrification.…”

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confidence: 99%

Isotopic signals of summer denitrification in a northern hardwood forested catchment

Wexler

Goodale

McGuire

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Despite decades of measurements, the nitrogen balance of temperate forest catchments remains poorly understood. Atmospheric nitrogen deposition often greatly exceeds streamwater nitrogen losses; the fate of the remaining nitrogen is highly uncertain. Gaseous losses of nitrogen to denitrification are especially poorly documented and are often ignored. Here, we provide isotopic evidence (δ 15 N NO3 and δ 18 O NO3 ) from shallow groundwater at the Hubbard Brook Experimental Forest indicating extensive denitrification during midsummer, when transient, perched patches of saturation developed in hillslopes, with poor hydrological connectivity to the stream, while streamwater showed no isotopic evidence of denitrification. During small rain events, precipitation directly contributed up to 34% of streamwater nitrate, which was otherwise produced by nitrification. Together, these measurements reveal the importance of denitrification in hydrologically disconnected patches of shallow groundwater during midsummer as largely overlooked control points for nitrogen loss from temperate forest catchments.M any forested catchments export far less nitrogen (N) in streamwater than they receive in atmospheric deposition (1, 2). The rest of the deposited N may accumulate in vegetation or soil organic matter, or be lost in gaseous form. Losses of N to denitrification, the microbial reduction of aqueous nitrate (NO 3 − ) to nitrous oxide (N 2 O, a greenhouse gas) and N 2 gas, are extremely difficult to measure due to the difficulty in directly measuring N 2 fluxes and due to the high degree of spatiotemporal variability in redox conditions and substrate sources (3). Many past studies using a range of measurements (streamwater nitrate isotopic composition, the acetylene block technique, N 2 O emissions, and mass balance calculations) have concluded that denitrification in temperate forests is highly uncertain or generally unimportant (e.g., refs. 4-8).Nitrogen budgets are particularly perplexing in the northern hardwood forests at the Hubbard Brook Experimental Forest (HBEF) in the White Mountains of New Hampshire, USA, where atmospheric deposition has supplied 6-8 kg N ha −1 ·yr −1 for half a century, a rate ∼5-10 times preindustrial levels (7-10). Accumulation of N in plant biomass ceased in the early 1990s (10, 11), while streamwater inorganic N export from catchments across the HBEF and nearby streams decreased to <1 kg N ha −1 ·yr −1 , for reasons that remain elusive (9,10,12). These N flux measurements imply increasingly important roles for N gas loss or storage in soil organic matter. However, both processes are so difficult to quantify that the fate, drivers, and consequences of the "missing" N remain unknown, at the HBEF and elsewhere (8)(9)(10)12 Table S1).Nitrate isotopic composition reflects not only NO 3 − sources but also fractionation from a range of processes (14, Table S1), including the HBEF (10, 17), have revealed little if any isotopic evidence of denitrification. SignificanceDenitrification is the most poorly under...

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Nitrogen and oxygen isotope fractionation during dissimilatory nitrate reduction by denitrifying bacteria

Cited by 391 publications

References 54 publications

Enrichment and characterization of ammonia-oxidizing archaea from the open ocean: phylogeny, physiology and stable isotope fractionation

Enrichment and characterization of ammonia-oxidizing archaea from the open ocean: phylogeny, physiology and stable isotope fractionation

An eddy-stimulated hotspot for fixed nitrogen-loss from the Peru oxygen minimum zone

Isotopic signals of summer denitrification in a northern hardwood forested catchment

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