The Biogeochemical Methane Cycle

Whiticar, Michael J.

doi:10.1007/978-3-319-90569-3_5

Cited by 22 publications

(21 citation statements)

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“…The pathways for carbon and electron flux in methanogenic environments are of interest because of the biogeochemical significance of methane production in diverse soils and sediments as well as the importance of anaerobic digestion as a bioenergy strategy ( 1 , 2 ). Diverse communities of bacteria convert complex organic matter primarily to acetate and carbon dioxide, which are then converted by methanogenic archaea to methane.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms for Electron Uptake by Methanosarcina acetivorans during Direct Interspecies Electron Transfer

Holmes

Zhou

Ueki

et al. 2021

mBio

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Section: Introductionmentioning

confidence: 99%

Mechanisms for Electron Uptake by Methanosarcina acetivorans during Direct Interspecies Electron Transfer

Holmes

Zhou

Ueki

et al. 2021

mBio

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“…In the sediment, upward rising CH 4 and downward diffusing SO 4 2− meet in the so-called sulfate-methane transition zone (SMTZ), where anaerobic methanotrophic archaea in syntrophic association with sulfate-reducing bacteria are able to reverse methanogenesis and oxidize CH 4 using SO 4 2− (Boetius et al, 2000). In most freshwater environments, low SO 4 2− FIGURE 6 2-dimensional isotope plot of sedimentary CH 4 data from the stratification and mixing period implemented into the classification of methanogenic pathways modified after (Whiticar, (2020). The dotted lines represent the range of ratios of 13 C and 2 H (C:D) enrichment during anaerobic CH 4 oxidation as reported by Martens et al (1999), Holler et al (2009 and Rasigraf et al (2012).…”

Section: Anaerobic Methane Oxidation In the Sedimentmentioning

confidence: 99%

“…Although the determination of dissolved CH 4 concentrations and CH 4 fluxes is helpful to establish the magnitude of emissions, it cannot resolve the responsible pathways and production mechanisms (Cadieux et al, 2016). Measurement of stable carbon and hydrogen isotopes of CH 4 (expressed as δ 13 C-CH 4 and δ 2 H-CH 4 values) are known to assist with identifying sources and sinks of CH 4 (e.g., Waldron et al, 1999;Whiticar, 2020;Douglas et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Application of concentration and 2-dimensional stable isotope measurements of methane to constrain sources and sinks in a seasonally stratified freshwater lake

Einzmann

Schroll

Kleint

et al. 2022

Front. Environ. Sci.

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Methane (CH4) emissions from aquatic systems have recently been comprised to account for up to 50% of global CH4 emissions, with lakes representing one of the largest CH4 sources within this pool. However, there is large uncertainty associated with CH4 emissions from freshwater environments to the atmosphere, because of a lack of understanding in the spatial and temporal dynamics of CH4 sources and sinks, as well as underlying mechanisms and processes. In this study, we investigated the concentrations and stable carbon (δ13C-CH4) and hydrogen (δ2H-CH4) isotope composition of CH4 in a small eutrophic lake (Lake Willersinnweiher) with seasonal stratification and its spatial and temporal variation. We found that while supersaturation of CH4 in the entire water column was present throughout the whole year, the isotopic composition of CH4 in sediment and water column varied depending on lake stratification, physiochemical conditions, and lake depth. During the stratification period, isotopic characteristics of pelagic surface water CH4 differed from littoral and sedimentary CH4, suggesting likely mixing of CH4 from different sources including vertical and lateral input as well as groundwater input and potentially oxic methane production in the mixed surface water layer. Aerobic CH4 oxidation indicated by a strong increase in both δ13C-CH4 and δ2H-CH4 values at the bottom of the oxycline was found to significantly reduce upward migrating CH4 released at the sediment-water interface. In the sediment, stable isotope characteristics of CH4 showed an increasing dominance of the acetoclastic CH4 formation pathway from the pelagic towards the littoral area. Furthermore, the occurrence of sulfate-dependent anaerobic methane oxidation in the sediment was suggested by an increase in δ13C-CH4 and δ2H-CH4 values. During the mixing period, the isotopic CH4 composition of the water column was distinctively less negative than during the stratification period potentially resulting from a greater impact of groundwater CH4 input compared to the stratification period. Our findings implicate that the application of concentrations and dual isotope measurements of CH4 is a promising approach for constraining CH4 sinks and sources in Lake Willersinnweiher and potentially other small lakes to clearly disentangle the complex CH4 dynamics in lakes both spatially and seasonally.

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“…The pathways for carbon and electron flux in methanogenic environments are of interest because of the biogeochemical significance of methane production in diverse soils and sediments as well as the importance of anaerobic digestion as a bioenergy strategy (1, 2). Diverse communities of bacteria convert complex organic matter primarily to acetate and carbon dioxide that are then converted by methanogenic archaea to methane.…”

Section: Introductionmentioning

confidence: 99%

Mechanisms for Electron Uptake byMethanosarcina acetivoransDuring Direct Interspecies Electron Transfer

Holmes

Zhou

Ueki

et al. 2021

Preprint

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Direct interspecies electron transfer (DIET) between bacteria and methanogenic archaea appears to be an important syntrophy in both natural and engineered methanogenic environments. However, the electrical connections on the outer surface of methanogens and the subsequent processing of electrons for carbon dioxide reduction to methane are poorly understood. Here we report that the genetically tractable methanogen Methanosarcina acetivorans can grow via DIET in co-culture with Geobacter metallireducens serving as the electron-donating partner. Comparison of gene expression patterns in M. acetivorans grown in co-culture versus pure culture growth on acetate revealed that transcripts for the outer-surface, multi-heme, c-type cytochrome MmcA were higher during DIET-based growth. Deletion of mmcA inhibited DIET. The high aromatic amino acid content of M. acetivorans archaellins suggests that they might assemble into electrically conductive archaella. A mutant that could not express archaella was deficient in DIET. However, this mutant grew in DIET-based co-culture as well as the archaella-expressing parental strain in the presence of granular activated carbon, which was previously shown to serve as a substitute for electrically conductive pili as a conduit for long-range interspecies electron transfer in other DIET-based co-cultures. Transcriptomic data suggesting that the membrane-bound Rnf, Fpo, and HdrED complexes also play a role in DIET were incorporated into a charge-balanced model illustrating how electrons entering the cell through MmcA can yield energy to support growth from carbon dioxide reduction. The results are the first genetics-based functional demonstration of likely outer-surface electrical contacts for DIET in a methanogen.

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The Biogeochemical Methane Cycle

Cited by 22 publications

References 532 publications

Mechanisms for Electron Uptake by Methanosarcina acetivorans during Direct Interspecies Electron Transfer

Mechanisms for Electron Uptake by Methanosarcina acetivorans during Direct Interspecies Electron Transfer

Application of concentration and 2-dimensional stable isotope measurements of methane to constrain sources and sinks in a seasonally stratified freshwater lake

Mechanisms for Electron Uptake byMethanosarcina acetivoransDuring Direct Interspecies Electron Transfer

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