Steady-State Nitrogen Isotope Effects of N2 and N2O Production in Paracoccus denitrificans

1999 ◽  
Vol 65 (3) ◽  
pp. 989-994 ◽  
Author(s):  
Carol C. Barford ◽  
Joseph P. Montoya ◽  
Mark A. Altabet ◽  
Ralph Mitchell
Keyword(s):  
Steady State ◽  
Stable Isotope ◽  
Isotope Effect ◽  
Paracoccus Denitrificans ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Dissolved Oxygen Concentration ◽  
Nitrogen Stable Isotope ◽  
N2o Production ◽  
Oxide Substrates

ABSTRACT Nitrogen stable-isotope compositions (δ15N) can help track denitrification and N2O production in the environment, as can knowledge of the isotopic discrimination, or isotope effect, inherent to denitrification. However, the isotope effects associated with denitrification as a function of dissolved-oxygen concentration and their influence on the isotopic composition of N2O are not known. We developed a simple steady-state reactor to allow the measurement of denitrification isotope effects in Paracoccus denitrificans. With [dO2] between 0 and 1.2 μM, the N stable-isotope effects of NO3 − and N2O reduction were constant at 28.6‰ ± 1.9‰ and 12.9‰ ± 2.6‰, respectively (mean ± standard error,n = 5). This estimate of the isotope effect of N2O reduction is the first in an axenic denitrifying culture and places the δ15N of denitrification-produced N2O midway between those of the nitrogenous oxide substrates and the product N2 in steady-state systems. Application of both isotope effects to N2O cycling studies is discussed.

The imprint of anammox on the stable isotope compositions of nitrogen-bearing molecules

2020 ◽  
Author(s):  
Paul Magyar ◽  
Damian Hausherr ◽  
Robert Niederdorfer ◽  
Jing Wei ◽  
Joachim Mohn ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotope Effect ◽  
Redox Reactions ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Biological Processes ◽  
Fixed Nitrogen ◽  
Ecological Complexity ◽  
Anammox Process ◽  
Isotope Measurements

<p>Stable isotope measurements of nitrogen and oxygen in nitrogen-containing molecules provide important constraints on the sources, sinks and pools of these molecules in the environment. Anammox is one of two known biological processes for converting fixed nitrogen to N<sub>2</sub>, and through its consumption of ammonium and nitrite and production of nitrate, it impacts the supply of a wide variety of fixed N molecules. Nevertheless, the isotope fractionations associated with the various anammox-associated redox reactions remain poorly constrained. We have measured the isotope effects of anammox in microbial communities enriched for the purpose of nitrogen removal from wastewater by anammox. In this system, we can replicate the ecological complexity exhibited in environmental settings, while also performing controlled experiments. We find that under a variety of conditions, the nitrogen isotope effect for the anaerobic oxidation of ammonium in this system (NH<sub>4</sub><sup>+ </sup>to N<sub>2</sub>) is between 19‰ and 32‰, that for the reduction of nitrite (NO<sub>2</sub><sup>–</sup> to N<sub>2</sub>) is between 7‰ and 18‰, and that for the production of nitrate (NO<sub>2</sub><sup>–</sup> to NO<sub>3</sub><sup>–</sup>) is between -16‰ and -43‰. We propose that these ranges reflect both (1) a mixture of signals from different anammox-performing species and (2) variation of the isotope effect associated with the anammox process within a given microbial community under different conditions. We seek to understand further what factors control this variability to better interpret stable isotope measurements of N-bearing molecules in environmental settings.</p>

Steady-State Oxygen Isotope Effects of N2O Production in Paracoccus denitrificans

2017 ◽  
Vol 74 (3) ◽  
pp. 507-509 ◽  
Author(s):  
Carol Barford ◽  
Joseph Montoya ◽  
Mark Altabet ◽  
Ralph Mitchell
Keyword(s):  
Steady State ◽  
Oxygen Isotope ◽  
Paracoccus Denitrificans ◽  
Isotope Effects ◽  
N2o Production

scholarly journals Nitrogen isotope effects can be used to diagnose N transformations in wastewater anammox systems

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paul M. Magyar ◽  
Damian Hausherr ◽  
Robert Niederdorfer ◽  
Nicolas Stöcklin ◽  
Jing Wei ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Isotope Composition ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Anammox Bacteria ◽  
Ammonium Oxidation ◽  
Experimental Conditions ◽  
N Transformations ◽  
Natural Systems ◽  
Inverse Isotope Effect

AbstractAnaerobic ammonium oxidation (anammox) plays an important role in aquatic systems as a sink of bioavailable nitrogen (N), and in engineered processes by removing ammonium from wastewater. The isotope effects anammox imparts in the N isotope signatures (15N/14N) of ammonium, nitrite, and nitrate can be used to estimate its role in environmental settings, to describe physiological and ecological variations in the anammox process, and possibly to optimize anammox-based wastewater treatment. We measured the stable N-isotope composition of ammonium, nitrite, and nitrate in wastewater cultivations of anammox bacteria. We find that the N isotope enrichment factor 15ε for the reduction of nitrite to N2 is consistent across all experimental conditions (13.5‰ ± 3.7‰), suggesting it reflects the composition of the anammox bacteria community. Values of 15ε for the oxidation of nitrite to nitrate (inverse isotope effect, − 16 to − 43‰) and for the reduction of ammonium to N2 (normal isotope effect, 19–32‰) are more variable, and likely controlled by experimental conditions. We argue that the variations in the isotope effects can be tied to the metabolism and physiology of anammox bacteria, and that the broad range of isotope effects observed for anammox introduces complications for analyzing N-isotope mass balances in natural systems.

scholarly journals Oxygen isotope fractionation during N<sub>2</sub>O production by soil denitrification

2016 ◽  
Vol 13 (4) ◽  
pp. 1129-1144 ◽  
Author(s):  
Dominika Lewicka-Szczebak ◽  
Jens Dyckmans ◽  
Jan Kaiser ◽  
Alina Marca ◽  
Jürgen Augustin ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Soil Water ◽  
Isotope Effect ◽  
Isotope Exchange ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
N2o Production ◽  
Oxygen Isotope Fractionation ◽  
Oxygen Isotope Exchange ◽  
Incubation Experiments

Abstract. The isotopic composition of soil-derived N2O can help differentiate between N2O production pathways and estimate the fraction of N2O reduced to N2. Until now, δ18O of N2O has been rarely used in the interpretation of N2O isotopic signatures because of the rather complex oxygen isotope fractionations during N2O production by denitrification. The latter process involves nitrate reduction mediated through the following three enzymes: nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR). Each step removes one oxygen atom as water (H2O), which gives rise to a branching isotope effect. Moreover, denitrification intermediates may partially or fully exchange oxygen isotopes with ambient water, which is associated with an exchange isotope effect. The main objective of this study was to decipher the mechanism of oxygen isotope fractionation during N2O production by soil denitrification and, in particular, to investigate the relationship between the extent of oxygen isotope exchange with soil water and the δ18O values of the produced N2O. In our soil incubation experiments Δ17O isotope tracing was applied for the first time to simultaneously determine the extent of oxygen isotope exchange and any associated oxygen isotope effect. We found that N2O formation in static anoxic incubation experiments was typically associated with oxygen isotope exchange close to 100 % and a stable difference between the 18O ∕ 16O ratio of soil water and the N2O product of δ18O(N2O ∕ H2O)  =  (17.5 ± 1.2) ‰. However, flow-through experiments gave lower oxygen isotope exchange down to 56 % and a higher δ18O(N2O ∕ H2O) of up to 37 ‰. The extent of isotope exchange and δ18O(N2O ∕ H2O) showed a significant correlation (R2 = 0.70, p <  0.00001). We hypothesize that this observation was due to the contribution of N2O from another production process, most probably fungal denitrification. An oxygen isotope fractionation model was used to test various scenarios with different magnitudes of branching isotope effects at different steps in the reduction process. The results suggest that during denitrification, isotope exchange occurs prior to isotope branching and that this exchange is mostly associated with the enzymatic nitrite reduction mediated by NIR. For bacterial denitrification, the branching isotope effect can be surprisingly low, about (0.0 ± 0.9) ‰, in contrast to fungal denitrification where higher values of up to 30 ‰ have been reported previously. This suggests that δ18O might be used as a tracer for differentiation between bacterial and fungal denitrification, due to their different magnitudes of branching isotope effects.

Isotope Effect Studies on Elimination Reactions. XI. The Nature of the Transition State for the E2 Reaction of 2-Phenylethyldimethylanilinium Salts Containing Substituents in the Aniline Ring with Sodium Ethoxide in Ethanol

1975 ◽  
Vol 53 (23) ◽  
pp. 3513-3525 ◽  
Author(s):  
Peter Schmid ◽  
Arthur Newcombe Bourns
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Structural Changes ◽  
Isotope Effects ◽  
Sodium Ethoxide ◽  
Nitrogen Isotope ◽  
Structural Variations ◽  
Hydrogen Deuterium ◽  
Elimination Reactions ◽  
Pass Through

Kinetic isotope effects have been determined for the E2 reactions of a series of 2-phenylethyldimethylanilinium salts containing substituents in the aniline ring with sodium ethoxide in ethanol at 40 °C. The nitrogen isotope effect, (k14/k15−1)100, is not very sensitive to substituent changes but appears to increase slightly with increasing electron-withdrawing ability of the substituents, i.e., 1.19 ± 0.07, 1.13 ± 0.06, 1.12 ± 0.08, 1.30 ± 0.07, and 1.32 ± 0.06 for p-OCH3, p-CH3, p-H, p-Cl, and, m-CF3, respectively. The hydrogen–deuterium isotope effects pass through a minimum in the region of the unsubstituted compound and increase both with increasing electron-donating as well as with electron-withdrawing power of the substituents, i.e. kH/kD = 4.70 ± 0.06, 4.61 ± 0.04, 4.51 ± 0.04, 4.53 ± 0.09, 5.00 ± 0.07, and 5.39 ± 0.07 for p-OCH3, p-CH3, p-H, p-Cl, m-CF3, and p-CF3, respectively. The results are discussed in terms of recent theoretical treatments of the effect of structural variations in the reactants on the nature of the transition state of E2 elimination reactions. The conclusion is reached that the transition states in the present reaction series can be characterized as 'central with slight carbanion character' and that the effect of a change in the ability of the leaving group on the structure of the transition state manifests itself mainly in the direction perpendicular to the reaction coordinate. A simple novel hypothesis is formulated which emphasizes the importance of the location of the transition state in a More O'Ferrall-type potential energy diagram in determining its sensitivity to structural changes in the reactants.

scholarly journals Quantitative Ecological Impact Assessments using  Natural Abundance Carbon and Nitrogen Stable Isotope Signatures

2021 ◽  
Author(s):  
◽  
Bruce David Dudley
Keyword(s):  
Stable Isotope ◽  
Nitrogen Isotope ◽  
High Light ◽  
Rocky Reef ◽  
Sewage Effluent ◽  
Light Conditions ◽  
Nitrogen Stable Isotope ◽  
Low Light ◽  
Carbon And Nitrogen ◽  
Reef Community

<p>The use of delta15N and delta13C signatures to infer sources of enrichment in ecological systems relies on predictability in the transfer of delta15N and delta13C ratios. This thesis examines patterns of delta15N and delta13C change as pools of nitrogen and carbon move from a sewage effluent discharge into organisms in an adjacent coastal rocky reef community (Titahi Bay, New Zealand). These changes and their mechanisms are examined in the broader context of current research using carbon and nitrogen stable isotope ratios in marine ecology, with particular reference to impact assessment. Firstly this thesis examines the assimilation of nitrogen and carbon isotopes in Ulva sp. under varying light conditions and nitrogen source (e.g., nitrate or ammonium). In a field study, algae grown at depth and under lower light conditions showed comparatively lighter nitrogen isotope signatures relative to the predicted concentration of available 15N-enriched sewage nitrogen. In a complementary laboratory experiment, results from manipulated light availability and N source (either nitrate or ammonium, in equivalent molar concentrations) suggest that: 1) low-light conditions can produce algae with lighter nitrogen isotope signatures; and 2) this effect was more pronounced for ammonium (3.7 per mil difference between high light and low light treatments) than for nitrate (0.6 per mil difference between high light and low light treatments) sources. Stable carbon isotope ratios (delta13C) of Ulva sp.grown in conditions of low nitrogen availability were shown to be generally lower than those grown in nitrogen rich conditions in both field and laboratory studies. Where nitrogen supply was sufficient for growth, low light conditions also produced generally lower delta13C signatures than high light conditions. Experimental trials with a uniform dissolved inorganic carbon source and altered light and nitrogen enrichment levels produced delta 13C levels in Ulva sp. tissue that spanned the recorded delta13C ranges of many common algal species; -5.99 per mil (high light, with added ammonium and phosphate) to -17.61 per mil (high light without nutrient additions). Chapter 3 of this study examines the growth response of Ulva sp. to surplus nitrate and ammonium (the two most common forms of nitrogen available to plants in seawater), under light limited conditions. Ulva sp. experienced a temporary reduction in growth rate and nitrogen assimilation capacity (shown in tissue nitrogen indices) when grown on nitrate, relative to ammonium. The magnitude and the temporary nature of these results suggest that in natural populations the relative proportion of nitrate or ammonium available is unlikely to significantly affect the growth capacity of Ulva sp. In chapter 4, I use delta13C and delta15N signatures to separately trace the dissolved and particulate fractions of sewage effluent dispersal onto a rocky reef community. Delta15N signatures from tissue of the macroalga Carpophyllum maschalocarpum, and the herbivorous isopod Amphoroidea media tracked the distribution and signature of DIN from a sewage treatment plant that generated heavy delta15N signatures. Delta13C signatures from tissue of the filter-feeding half-crab Petrolisthes elongatus tracked the distribution and signature of suspended sewage particulate organic matter.</p>

Isotope Effect Studies on Elimination Reactions. IX. The Nature of the Transition State for the E2 Reaction of 2-Arylethylammonium Ions with Ethoxide in Ethanol

1974 ◽  
Vol 52 (5) ◽  
pp. 749-760 ◽  
Author(s):  
P. J. Smith ◽  
A. N. Bourns
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Kinetic Isotope Effects ◽  
Ammonium Ions ◽  
Nitrogen Effect ◽  
Kinetic Isotope ◽  
Leaving Group ◽  
Hydrogen Deuterium

Kinetic isotope effects have been determined for the E2 reaction of some 2-arylethyltrimethyl-ammonium ions with ethoxide in ethanol at 40°. The nitrogen effect, (k14/k15 − 1)100, decreased with increasing electron-withdrawing ability of the para substituent; i.e. 1.37, 1.33, 1.14, and 0.88 for p-OCH3, p-H, p-Cl, and p-CF3, respectively. Furthermore, the primary hydrogen–deuterium isotope effects increased for the same substituents, respectively; i.e. kH/kD = 2.64, 3.23, 3.48, and 4.16. A large positive ρ value of 3.66 was found as well as a small secondary α-deuterium effect of 1.02 for p-H. In addition, the nitrogen isotope effect decreased with increasing strength of the abstracting base for the reaction of ethyltrimethylammonium ion; i.e. 1.86 and 1.41 at 60° for reaction with EtO−–EtOH and t-BuO−–t-BuOH, respectively. The results are discussed in terms of recent theoretical treatments of the effect of base, substituents, and nature of the leaving group on the nature of the transition state for an E2 process. The conclusion is reached that any structural change which causes one bond (C—H) to be weakened more at the transition state will have a corresponding effect on the other bond [Formula: see text]

scholarly journals Dry or Wet? Evaluating the Initial Rice Cultivation Environment on the Korean Peninsula

Agronomy ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 929
Author(s):  
Shinya Shoda ◽  
Hiroo Nasu ◽  
Kohei Yamazaki ◽  
Natsuki Murakami ◽  
Geon-Ju Na ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Bronze Age ◽  
Isotope Analysis ◽  
Nitrogen Isotope ◽  
Rice Cultivation ◽  
Nitrogen Stable Isotope ◽  
Carbon And Nitrogen ◽  
The Difference ◽  
Potential Factors ◽  
Cultivation Environment

The origins and development of rice cultivation are one of the most important aspects in studying agricultural and socio-economic innovations, as well as environmental change, in East Asian prehistory. In particular, whether wet or dry rice cultivation was conducted is an important consideration of its impact on societies and the environment across different periods and places. In this study, carbon and nitrogen stable isotope analysis of charred crop remains from archaeological sites dating from the Early Bronze Age (ca. 1.1k BC) to the Proto-Three Kingdoms (ca. 0.4 k AD) was conducted to clarify: (1) if there were any shifts from dry to wet cultivation around 1500 years after rice adoption as previously hypothesized and (2) the difference in stable carbon and nitrogen isotope values between rice and dry fields crops excavated from the same archaeological context to understand the cultivation environment. The result show that stable isotope values of charred rice grains have not changed significantly for around 1500 years. Moreover, rice possessed higher nitrogen stable isotope values than dry crops across all periods. While other potential factors could have influenced the 15N-enrichment of soils and crops, the most reasonable explanation is bacteriologic denitrification in anaerobic paddy soil where the rice was grown.

scholarly journals Isotope fractionation (δ 13C, δ15N) and microbial community response in degradation of petroleum hydrocarbons by biostimulation in contaminated soil

2021 ◽  
Author(s):  
Heng Liu ◽  
Manli Wu ◽  
Xiqian Guo ◽  
Huan Gao ◽  
Yinrui Xu
Keyword(s):  
Isotope Effect ◽  
Contaminated Soil ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Alpha Diversity ◽  
Nitrogen Isotope ◽  
Community Response ◽  
Carbon And Nitrogen ◽  
Stable Isotope Fractionation ◽  
Compost Amendment

Abstract This study investigated the isotope effects of δ13C and δ15N and microbial response during biodegradation of hydrocarbons by biostimulation with nitrate or compost in the petroleum-contaminated soil. Compost and KNO3 amendments promoted the total petroleum hydrocarbon (TPH) removal accompanied by a significant increase of Actinobacteria and Firmicutes phyla. Soil alpha diversity decreased after 90 days of biostimulation. An inverse significant carbon isotope effect (εc = 16.6 ± 0.8‰) and strong significant nitrogen isotope effect (εN = -24.20 ± 9.54‰) were shown by the KNO3 supplementation. For compost amendment, significant carbon and nitrogen isotope effect were εc = 38.8 ± 1.1‰ and εN = -79.49 ± 16.41‰, respectively. A clear difference of the carbon and nitrogen stable isotope fractionation was evident by KNO3 or compost amendment, which indicated the mechanisms of petroleum degradation by adding compost or KNO3 are different.

scholarly journals The mechanism of oxygen isotope fractionation during N<sub>2</sub>O production by denitrification

2015 ◽  
Vol 12 (20) ◽  
pp. 17009-17049
Author(s):  
D. Lewicka-Szczebak ◽  
J. Dyckmans ◽  
J. Kaiser ◽  
A. Marca ◽  
J. Augustin ◽  
...  
Keyword(s):  
Oxygen Isotope ◽  
Soil Water ◽  
Isotope Effect ◽  
Isotope Exchange ◽  
Isotope Fractionation ◽  
Isotope Effects ◽  
Nitrite Reduction ◽  
N2o Production ◽  
Oxygen Isotope Fractionation ◽  
Oxygen Isotope Exchange

Abstract. The isotopic composition of soil-derived N2O can help differentiate between N2O production pathways and estimate the fraction of N2O reduced to N2. Until now, δ18O of N2O has been rarely used in the interpretation of N2O isotopic signatures because of the rather complex oxygen isotope fractionations during N2O production by denitrification. The latter process involves nitrate reduction mediated through the following three enzymes: nitrate reductase (NAR), nitrite reductase (NIR) and nitric oxide reductase (NOR). Each step removes one oxygen atom as water (H2O), which gives rise to a branching isotope effect. Moreover, denitrification intermediates may partially or fully exchange oxygen isotopes with ambient water, which is associated with an exchange isotope effect. The main objective of this study was to decipher the mechanism of oxygen isotope fractionation during N2O production by denitrification and, in particular, to investigate the relationship between the extent of oxygen isotope exchange with soil water and the δ18O values of the produced N2O. We performed several soil incubation experiments. For the first time, Δ17O isotope tracing was applied to simultaneously determine the extent of oxygen isotope exchange and any associated oxygen isotope effect. We found bacterial denitrification to be typically associated with almost complete oxygen isotope exchange and a stable difference in δ18O between soil water and the produced N2O of δ18O(N2O / H2O) = (17.5 ± 1.2) ‰. However, some experimental setups yielded oxygen isotope exchange as low as 56 % and a higher δ18O(N2O / H2O) of up to 37 ‰. The extent of isotope exchange and δ18O(N2O / H2O) showed a very significant correlation (R2 = 0.70, p < 0.00001). We hypothesise that this observation was due to the contribution of N2O from another production process, most probably fungal denitrification. An oxygen isotope fractionation model was used to test various scenarios with different magnitudes of branching isotope effects at different steps in the reduction process. The results suggest that during denitrification the isotope exchange occurs prior to the isotope branching and that the mechanism of this exchange is mostly associated with the enzymatic nitrite reduction mediated by NIR. For bacterial denitrification, the branching isotope effect can be surprisingly low, about (0.0 ± 0.9) ‰; in contrast to fungal denitrification where higher values of up to 30 ‰ have been reported previously. This suggests that δ18O might be used as a tracer for differentiation between bacterial and fungal denitrification, due to their different magnitudes of branching isotope effects.

Sign in / Sign up

Export Citation Format

Share Document