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 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.

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.

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.

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 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.

THE MECHANISM OF THE CARBONYL ELIMINATION REACTION OF BENZYL NITRATE KINETIC ISOTOPE EFFECTS AND DEUTERIUM EXCHANGE

1960 ◽  
Vol 38 (12) ◽  
pp. 2457-2466 ◽  
Author(s):  
Erwin Buncel ◽  
A. N. Bourns
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Kinetic Isotope Effects ◽  
Deuterium Exchange ◽  
Elimination Reaction ◽  
Deuterium Isotope Effect ◽  
Nitrite Ion ◽  
Kinetic Isotope ◽  
Reaction Constant

The carbonyl elimination reaction (ECO2) of benzyl nitrate has been investigated with the object of distinguishing between the concerted and carbanion mechanisms. A deuterium exchange experiment resulted in a very small amount of deuterium pickup. The nitrogen isotope effect, k14/k15, associated with formation of the nitrite ion was found to be 1.0196 ± 0.0007 at 30 °C. The two results taken together exclude the formation of a carbanion intermediate but are consistent with a concerted mechanism.Benzyl-α-d2 nitrate has been prepared and the rate of its carbonyl elimination reaction compared with that of the undeuterated compound. The deuterium isotope effect was 5.04 ± 0.25 at 60 °C. The significance of the magnitude of the nitrogen and deuterium isotope effects and of their interrelationship with the Hammett reaction constant rho is discussed in terms of the nature of the transition state and a comparison is made with other E2 elimination reactions.

Isotope Effect Studies on Elimination Reactions. X. The Nature of The Transition State for the ECO2 Reaction of Para- substituted Benzyl Nitrates with Base in 90% by Volume Ethanol–Water

1975 ◽  
Vol 53 (9) ◽  
pp. 1319-1326 ◽  
Author(s):  
Peter James Smith ◽  
Carol Audrey Pollock ◽  
Arthur Newcombe Bourns
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Kinetic Isotope Effects ◽  
The Other ◽  
Theoretical Treatment ◽  
Kinetic Isotope ◽  
Hydrogen Deuterium ◽  
Deuterium Isotope Effects

Kinetic isotope effects have been determined for the Eco2 reaction of para-substituted benzyl nitrates with ethoxide in 90 vol.% ethanol–water at 20°. The nitrogen isotope effect, (k14/k15−1)100 decreased with increasing electron-withdrawing ability of the para-substituent; i.e. 2.26, 1.95, 1.60, and 0.84 for p-CH3, p-H, p-CF3, and p-NO2, respectively. Furthermore, the primary hydrogen–deuterium isotope effects increased also for electron-withdrawing substituents; i.e. kH/kD = 5.78, 6.06, 6.40, 6.67, and 7.05 for p-CH3, p-H, p-Br, p-CF3, and p-NO2, respectively. The results are discussed in terms of a recent theoretical treatment dealing with the effect of substituents on the nature of the transition state for a concerted E2 process. The conclusion is reached that any structural change which causes one bond (carbon–hydrogen) to be weakened more at the transition state will have a corresponding effect on the other bond (oxygen–nitrogen).

scholarly journals Viewpoint: Isotopic fractionation by plant nitrate reductase, twenty years later

2006 ◽  
Vol 33 (6) ◽  
pp. 531 ◽  
Author(s):  
Guillaume Tcherkez ◽  
Graham D. Farquhar
Keyword(s):  
Nitrate Reductase ◽  
Isotope Effect ◽  
Nitrate Reduction ◽  
Isotope Effects ◽  
Isotopic Fractionation ◽  
Nitrogen Isotope ◽  
Reaction Rates ◽  
Rate Limiting Step ◽  
18O Isotope ◽  
N Isotopes

Plant nitrate reductase, the enzyme that reduces nitrate (NO3–) to nitrite (NO2–), is known to fractionate N isotopes, depleting nitrite in 15N compared with substrate nitrate. Nearly 20 years ago, the nitrogen isotope effect associated with this reaction was found to be around 1.015. However, the relationships between the isotope effect and the mechanism of the reaction have not yet been examined in the light of recent advances regarding the catalytic cycle and enzyme structure. We thus give here the mathematical bases of the 14N / 15N and also the 16O / 18O isotope effects as a function of reaction rates. Enzymatic nitrate reduction involves steps other than NO3– reduction itself, in which the oxidation number of N changes from +V (nitrate) to +III (nitrite). Using some approximations, we give numerical estimates of the intrinsic N and O isotope effects and this leads us to challenge the assumptions of nitrate reduction itself as being a rate-limiting step within the nitrate reductase reaction, and of the formation of a bridging oxygen as a reaction intermediate.

ISOTOPE EFFECT STUDIES ON ELIMINATION REACTIONS: V. THE MECHANISM OF THE CARBONYL ELIMINATION REACTION OF 9-FLUORENYL NITRATE WITH ACETATE ION

1966 ◽  
Vol 44 (21) ◽  
pp. 2553-2561 ◽  
Author(s):  
P. J. Smith ◽  
A. N. Bourns
Keyword(s):  
Isotope Effect ◽  
Isotope Effects ◽  
Nitrogen Isotope ◽  
Deuterium Exchange ◽  
Anhydrous Ethanol ◽  
Elimination Reaction ◽  
Reaction Conditions ◽  
Two Stage ◽  
Deuterium Isotope Effects ◽  
Intermediate Mechanism

The carbonyl elimination reaction (ECO2) of 9-fluorenyl nitrate with acetate ion in anhydrous ethanol was found to be second order and to give at 30° primary nitrogen-15 and deuterium isotope effects of 1.0091 ± 0.0007 and 4.3 ± 0.2, respectively. The ester showed no deuterium exchange with solvent under the reaction conditions. A change in solvent to 85 volume % ethanol–water increased the nitrogen isotope effect to 1.0131 ± 0.0007 without changing the deuterium effect. These results exclude any form of two-stage carbanion intermediate mechanism, but are in accord with a concerted process.

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