Low <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si35.svg"><mml:mrow><mml:mi mathvariant="normal">Δ</mml:mi><mml:msup><mml:mrow/><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msup><mml:msub><mml:mrow><mml:mi mathvariant="normal">CH</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi mathvariant="normal">D</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math> values in microbialgenic methane result from co

Taenzer, Lina; Labidi, Jabrane; Masterson, Andrew L.; Feng, Xiahong; Rumble, Douglas; Young, Edward; Leavitt, William D.

doi:10.1016/j.gca.2020.06.026

Cited by 40 publications

(32 citation statements)

References 37 publications

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“…The causes of the disequilibrium are beyond the scope of this study but may include: the rate of methanogenesis (e.g. Wang et al, 2015, Stolper et al, 2015, the metabolic pathways (Giunta et al, 2019;Young 2019), statistical combinatorial effects (Young et al, 2017;Cao et al, 2019;Taenzer et al, 2020), and/or quantum tunneling effects (Young et al, 2017;2019). In natural settings, disequilibrium signatures similar to those observed in laboratory are commonly observed (e.g.…”

Section: Isotope-bond Reorderingmentioning

confidence: 99%

Evidence for methane isotopic bond re-ordering in gas reservoirs sourcing cold seeps from the Sea of Marmara

Giunta

Labidi

Kohl

et al. 2021

Earth and Planetary Science Letters

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The measurement of methane clumped isotopologues (Δ 13 CH3D and Δ 12 CH2D2) allows exploring isotope bond ordering within methane molecules, and may reveal equilibrium temperatures. Whether such temperature reflects the formation or re-equilibration temperature of the methane is not well understood, but would have critical implications for the use of methane clumped isotopologues as geothermometers. Here we investigate gas bubbles from vigorous emissions at cold seeps (n = 14) in the Sea of Marmara, Turkey. These cold seeps are sourced from deeper sedimentary reservoirs. Conventional geochemical tracers such as carbon and hydrogen bulk isotopic ratios ( 13 C/ 12 C and D/H) or n-alkane molecular ratios, suggest these gases reflect various degrees of mixing between thermogenic and microbial sources. Some samples would generally be considered purely microbial in origin (C1/C2+ > 1500; δ 13 C < -60 ‰). We report measurements of Δ 13 CH3D and Δ 12 CH2D2 showing that a fraction of those gases are in internal thermodynamic equilibrium, with the abundances of the two mass-18 isotopologues indicating concordant temperatures of ~90 °C and ~130 °C . These concordant temperatures are recorded by gases of putative microbial and thermogenic origin; the temperatures of equilibration are irrespective of the formation mechanism of the gases. We conclude that the two high-temperatures recorded by Δ 13 CH3D and 1 *Manuscript Click here to view linked References Δ 12 CH2D2 are best explained by non-enzymatic re-equilibration at two local subsurface temperatures. First principles suggest that unequal rates of exchange is possible. Disequilibrium signatures where the two isotopologues yield discordant apparent temperatures are exhibited by other samples. In those cases the data define a trend of variable D 13 CH3D at nearly constant D 12 CH2D2. These signatures are enigmatic, and we investigate and reject multiple possible explanations including mixing, diffusion or Anaerobic Oxidation of Methane. Different rates of re-equilibration between the two rare isotopologues is implied, although lacks experimental foundation at present. In general, all of these data point towards reequilibration of the mass-18 methane isotopologues as an important process.

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Section: Isotope-bond Reorderingmentioning

confidence: 99%

Evidence for methane isotopic bond re-ordering in gas reservoirs sourcing cold seeps from the Sea of Marmara

Giunta

Labidi

Kohl

et al. 2021

Earth and Planetary Science Letters

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“…A recent non-peer-reviewed presentation reports isotopic contents of methane produced by the high temperature (600°C) pyrolysis of an ethane substrate, finding results broadly similar to those reported here (i.e., apparently equilibrated Δ 13 CH 3 D and highly-depleted Δ 12 CH 2 D 2 values; Eldridge et al, 2019b). It has also been shown recently that low-temperature Pseudomonas stutzeri cultures produce methane by combining a methyl group (formed by decomposing methylphosphonate, CH 3 O 3 P) and a hydrogen atom from water (Taenzer et al, 2020). The combinatorial effect can explain the observed Δ 13 CH 3 D and Δ 12 CH 2 D 2 values and is particularly clearly evidenced by variation of Δ 12 CH 2 D 2 between methane formed in the presence of waters of various hydrogen isotope compositions.…”

Section: Model Assumptions and Comparison Of Fitted Parameters With Prior Constraintsmentioning

confidence: 91%

“…This approximation leads to no analytically resolvable systematic errors provided 0<[D] A <0.001 and 0<[D] B <0.001 (i.e., when δD of both pools is < ~5400‰ -clearly true in the case of our experiments). This mechanism for producing exceptional clumped isotope ∆ values has been called the 'combinatorial effect' (Yeung, 2016;Röckmann et al, 2016;Clog et al, 2018;Cao et al, 2019;Xia and Gao, 2019;Taenzer et al, 2020). Such effects can arise any time two or more symmetrically equivalent molecular sites are created in such a way that they have different probabilities of containing a rare isotope substitution; these anomalies have been observed in microbial methane (Taenzer et al, 2020), and predicted for O 2 , N 2 (Yeung, 2016) and ethane (Clog et al, 2018), and should be expected for emerging clumped isotope systems like sulfate (Ueno et al, 2019;Neubauer et al, 2020), H 2 (Popa et al, 2019), perchlorate (Martin, 2020), nitrate (Neubauer et al, 2020), and ∆ 48 in CO 2 (Fiebig et al, 2019a;Bajnai et al, 2020).…”

Section: Rayleigh Distillations and The Combinatorial Effectmentioning

confidence: 99%

“…The combinatorial effect could also cause a deficit in Δ 12 CH 2 D 2 of microbial methane if hydrogen atoms source from two or more isotopically different pools, e.g., from water, a reduced hydrogen pool, sulfur-bonded hydrogen, or carbon-bonded hydrogen (Valentine et al, 2004;Scheller et al, 2013;Greening et al, 2016;Young et al, 2017;Giunta et al, 2019;Cao et al, 2019). In fact, a combinatorial effect has been observed and studied in methane production by Pseudomonas stutzeri cultures, as discussed in 4.2.2.4 (Taenzer et al, 2020).…”

Section: Implications For the Role Of The Combinatorial Effect In Abiogenesis And Biogenesis Of Methanementioning

confidence: 99%

“…Microbial methane can be produced by hydrogenotrophic and methylotrophic methanogenesis and consumed by methanotrophy through aerobic or anaerobic oxidation (Valentine et al, 2004;Valentine, 2011;Yoshinaga et al, 2014). These microbial metabolic processes can result in both equilibrated and non-equilibrated clumped isotope compositions in methane; both equilibrated and nonequilibrated compositions are common in natural environments, whereas all laboratory culture studies published to-date have produced non-equilibrium compositions (Wang et al, 2015;Stolper et al, 2015;Douglas et al, 2016;Young et al, 2017;Gruen et al, 2018;Giunta et al, 2019;Taenzer et al, 2020). Enzymatic reversibility has been proposed to control the expression of kinetic isotope effects during microbial methanogenesis.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Clumped isotope effects of thermogenic methane formation: Insights from pyrolysis of hydrocarbons

Dong

Xie

Formolo

et al. 2021

Geochimica et Cosmochimica Acta

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This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Archaeal lipid hydrogen isotopes in a marine thaumarchaeon

Leavitt

Kopf

Weber

et al. 2022

Preprint

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The stable hydrogen isotope composition of persistent biomolecules is used as a paleoenvironmental proxy. While much previous work has focused on plant leaf wax-derived n-alkanes, the potential of bacterial and archaeal lipid biomarkers as carriers of H isotope signatures remains underexplored. Here we investigated H isotope distributions in the membrane lipids of the ammonia-oxidizing chemoautotroph Nitrosopumilus maritimus strain SCM1. Hydrogen isotope ratios were measured on the biphytane chains of tetraether membrane lipids extracted from steady-state continuous cultures cultivated at slow, medium, and fast growth rates. In contrast to recent work on bacterial fatty acids, where the direction and magnitude of isotopic fractionation varies widely (ca. 600 energy metabolism, archaeal biphytane data in the present work are relatively invariant. The weighted average 2H/1H fractionation values relative to growth water (2εL/W) only ranged from 272 to 260 a three-fold difference in doubling times (30.8 hr to 92.5 hr), yielding an average growth-rate effect of 0.2 depleted than all heterotrophic archaeal and bacterial lipid H isotope measurements in the literature, and on par with those from other autotrophic archaea, as well as isoproenoid-based lipids in photoautotrophic algae. N. maritimus values of 2εL/W also varied systematically with the number of internal rings (cyclopentyl + cyclohexyl), increasing for each additional ring by 6.4 ± 2.7 an isotope flux-balance model in tandem with a comprehensive analysis of the sources of H in archaeal lipid biosynthesis, we use this observation to estimate the kinetic isotope effects (KIEs) of H incorporation from water; from reducing cofactors such as ferredoxin, and for the transhydrogenation reaction(s) that convert the electron-donor derived NADH into NADPH for anabolic reactions. Consistent with prior studies on bacteria, our results indicate the KIEs of reducing cofactors and transhydrogenation processes in archaea are highly fractionating, while those involving exchange of water protons are less so. When combined with the observation of minimal growth-rate sensitivity, our results suggest biphytanes of autotrophic 3HP/4HB Thaumarchaeota may be offset from source waters by a nearly constant 2εL/W value. Together with the ring effect, this implies that all biphytanes originating from a common source should have a predictable ordering of their isotope ratios with respect to biphytane ring number, allowing precise reconstruction of the original δ2H value of the growth water. Collectively, these patterns indicate archaeal biphytanes have potential as paleo-hydrological proxies, either as a complement or an alternative to leaf wax n-alkanes.

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Low Δ12CH2D2 values in microbialgenic methane result from co

Cited by 40 publications

References 37 publications

Evidence for methane isotopic bond re-ordering in gas reservoirs sourcing cold seeps from the Sea of Marmara

Evidence for methane isotopic bond re-ordering in gas reservoirs sourcing cold seeps from the Sea of Marmara

Clumped isotope effects of thermogenic methane formation: Insights from pyrolysis of hydrocarbons

Archaeal lipid hydrogen isotopes in a marine thaumarchaeon

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