Carbon isotope fractionation of Thermoanaerobacter kivui in different growth media and at different total inorganic carbon concentration

Blaser, Martin; Dreisbach, Lisa K.; Conrad, Ralf

doi:10.1016/j.orggeochem.2015.01.013

Cited by 10 publications

(6 citation statements)

References 51 publications

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“…The possibility of effects by bicarbonate or CO 2 concentrations, being different in the pure microbial cultures; the unbuffered and buffered soil suspensions; or phosphate effects should be considered. Effects of CO 2 concentrations and buffer systems on fractionation factors have for example been observed in cultures of chemolithoautotrophic Thermoanaerobacter kivui (Blaser et al, 2015).…”

Section: Methanogenic Conditionsmentioning

confidence: 99%

Fractionation of stable carbon isotopes during acetate consumption by methanogenic and sulfidogenic microbial communities in rice paddy soils and lake sediments

2021

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Abstract. Acetate is an important intermediate during the degradation of organic matter in anoxic flooded soils and sediments. Acetate is disproportionated to CH4 and CO2 by methanogenic or is oxidized to CO2 by sulfate-reducing microorganisms. These reactions result in carbon isotope fractionation, depending on the microbial species and their particular carbon metabolism. To learn more about the magnitude of the isotopic enrichment factors (ε) involved, acetate conversion to CH4 and CO2 was measured in anoxic paddy soils from Vercelli (Italy) and the International Rice Research Institute (IRRI, the Philippines) and in anoxic lake sediments from the northeastern and the southwestern basins of Lake Fuchskuhle (Germany). Acetate consumption was measured using samples of paddy soil or lake sediment suspended in water or in phosphate buffer (pH 7.0), both in the absence and presence of sulfate (gypsum), and of methyl fluoride (CH3F), an inhibitor of aceticlastic methanogenesis. Under methanogenic conditions, values of εac for acetate consumption were always in a range of −21 ‰ to −17 ‰ but higher in the lake sediment from the southwestern basin (−11 ‰). Under sulfidogenic conditions εac values tended to be slightly lower (−26 ‰ to −19 ‰), especially when aceticlastic methanogenesis was inhibited. Again, εac in the lake sediment of the southwestern basin was higher (−18 ‰ to −14 ‰). Determination of εCH4 from the accumulation of 13C in CH4 resulted in much lower values (−37 ‰ to −27 ‰) than from the depletion of 13C in acetate (−21 ‰ to −17 ‰ ), especially when acetate degradation was measured in buffer suspensions. The microbial communities were characterized by sequencing the bacterial 16S rRNA (ribosomal ribonucleic acid) genes as well as the methanogenic mcrA and sulfidogenic dsrB genes. The microbial communities were quite different between lake sediments and paddy soils but were similar in the sediments of the two lake basins and in the soils from Vercelli and the IRRI, and they were similar after preincubation without and with addition of sulfate (gypsum). The different microbial compositions could hardly serve for the prediction of the magnitude of enrichment factors.

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Section: Methanogenic Conditionsmentioning

confidence: 99%

Fractionation of stable carbon isotopes during acetate consumption by methanogenic and sulfidogenic microbial communities in rice paddy soils and lake sediments

2021

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“…Stable isotopic compositions of microbial lipids provide valuable metabolic and taxonomic information that helps to decipher the role of microorganisms in biogeochemical cycles (Hayes, 1993;Hinrichs et al, 1999;Dawson et al, 2015). The 13 C/ 12 C ratio, expressed as δ 13 C, of microbial biomass is primarily determined by the carbon sources, fixation pathways and physiological conditions (e.g., Hinrichs et al, 1999;Hayes, 2001;Boschker and Middelburg, 2002;Schouten et al, 2004;Londry et al, 2008;Blaser et al, 2015), whereas the ratio of stable hydrogen isotopes (deuterium/protium ratio; D/H; expressed as δD) is determined by the water and substrate-based sources of hydrogen and the interactions of central metabolic pathways (Valentine, 2009;Zhang et al, 2009a;Wijker et al, 2019). The fractionation factors that determine the δD value of lipids versus source water vary systematically with specific metabolisms, showing a decrease in the order: heterotrophic growth on TCA-cycle precursors and intermediates > heterotrophic growth on sugars > photoautotrophy > chemoautotrophy (Valentine et al, 2004a;Sessions and Hayes, 2005;Zhang et al, 2009a).…”

Section: Introductionmentioning

confidence: 99%

Substrate‐dependent incorporation of carbon and hydrogen for lipid biosynthesis by Methanosarcina barkeri

Meador

Könneke

et al. 2020

Environ Microbiol Rep

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Summary Dual stable isotope probing has been used to infer rates of microbial biomass production and modes of carbon fixation. In order to validate this approach for assessing archaeal production, the methanogenic archaeon Methanosarcina barkeri was grown either with H2, acetate or methanol with D2O and 13C‐dissolved inorganic carbon (DIC). Our results revealed unexpectedly low D incorporation into lipids, with the net fraction of water‐derived hydrogen amounting to 0.357 ± 0.042, 0.226 ± 0.003 and 0.393 ± 0.029 for growth on H2/CO2, acetate and methanol respectively. The variability in net water H assimilation into lipids during the growth of M. barkeri on different substrates is possibly attributed to different Gibbs free energy yields, such that higher energy yield promoted the exchange of hydrogen between medium water and lipids. Because NADPH likely serves as the portal for H transfer, increased NADPH production and/or turnover associated with high energy yield may explain the apparent differences in net water H assimilation into lipids. The variable DIC and water H incorporation into M. barkeri lipids imply systematic, metabolic patterns of isotope incorporation and suggest that the ratio of 13C‐DIC versus D2O assimilation in environmental samples may serve as a proxy for microbial energetics in addition to microbial production and carbon assimilation pathways.

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“…Recent evidence also suggests that for sulfatereducing bacteria, the overall isotope fractionation during sulfate reduction is influenced by all steps in the dissimilatory pathway (16,60). In contrast, differences in the substrate ratios of H 2 and CO 2 for acetogenic cultures did not affect fractionation (61). Furthermore, it has been shown that there is no intramolecular fractionation during acetate formation: the isotope values of the methyl group were similar to the ␦ 13 C values of the overall acetate signal (35).…”

Section: Discussionmentioning

confidence: 88%

Carbon Isotope Fractionation during Catabolism and Anabolism in Acetogenic Bacteria Growing on Different Substrates

Freude

Blaser

2016

Appl Environ Microbiol

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Homoacetogenic bacteria are versatile microbes that use the acetyl coenzyme A (acetyl-CoA) pathway to synthesize acetate from CO 2 and hydrogen. Likewise, the acetyl-CoA pathway may be used to incorporate other 1-carbon substrates (e.g., methanol or formate) into acetate or to homoferment monosaccharides completely to acetate. In this study, we analyzed the fractionation of pure acetogenic cultures grown on different carbon substrates. While the fractionation of Sporomusa sphaeroides grown on C 1 compounds was strong ( C1 , ؊49‰ to ؊64‰), the fractionation of Moorella thermoacetica and Thermoanaerobacter kivui using glucose ( Glu ‫؍‬ ؊14.1‰) was roughly one-third as strong, suggesting a contribution of less-depleted acetate from fermentative processes. For M. thermoacetica, this could indeed be validated by the addition of nitrate, which inhibited the acetyl-CoA pathway, resulting in fractionation during fermentation ( ferm ‫؍‬ ؊0.4‰). In addition, we determined the fractionation into microbial biomass of T. kivui grown on H 2 /CO 2 ( anabol. ‫؍‬ ؊28.6‰) as well as on glucose ( anabol. ‫؍‬ ؉2.9‰).A cetogenic bacteria are a widespread microbial group unified by their ability to use the reductive acetyl coenzyme A (acetylCoA) pathway, which allows chemolithoautotrophic growth on hydrogen and carbon dioxide and is the only known pathway that combines carbon dioxide fixation with energy conservation (1-6). Most acetogens can use the reductive acetyl-CoA pathway for autotrophic growth, reducing 2 carbon dioxide molecules with 4 hydrogen molecules to liberate 1 acetate molecule. Under these conditions, CO 2 reduction with H 2 yields a ⌬G o = value of Ϫ95 kJ/mol. This is barely enough to generate 1 ATP molecule using either a sodium-or a proton-dependent electron motive force (7). On the other hand, the acetyl-CoA pathway can be accompanied by the fermentation of carbon substrates. Under these autotrophic conditions, the energy yield for, e.g., glucose fermentation to 3 acetate molecules is expressed by the equation ⌬G o = ϭ Ϫ310.9 kJ/mol. In contrast to fermentations of glucose by most other anaerobes, which yield only 1 to 3 ATP molecules via substratelevel phosphorylation during glycolysis, acetogens can redirect the reducing equivalents to the reductive acetyl-CoA pathway, allowing the generation of an additional ATP molecule as described above (3,8).One approach to evaluating the contributions of different bacterial pathways to certain compound pools in environmental systems is to use the natural abundance of stable carbon isotopes to track the metabolic activity of certain microorganisms in the environment (9, 10): In principle, each metabolic pathway is characterized by a specific preference for a certain carbon isotope (usually the lighter 12 C) during catalysis, resulting in a characteristic depletion of 13 C between the substrate and the end product. Mathematically, this depletion is characterized by the so-called apparent fractionation factor (␣) or enrichment factor (ε); ε is calculated as 10 3 (1 Ϫ ␣). For...

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Carbon isotope fractionation of Thermoanaerobacter kivui in different growth media and at different total inorganic carbon concentration

Cited by 10 publications

References 51 publications

Fractionation of stable carbon isotopes during acetate consumption by methanogenic and sulfidogenic microbial communities in rice paddy soils and lake sediments

Fractionation of stable carbon isotopes during acetate consumption by methanogenic and sulfidogenic microbial communities in rice paddy soils and lake sediments

Substrate‐dependent incorporation of carbon and hydrogen for lipid biosynthesis by Methanosarcina barkeri

Carbon Isotope Fractionation during Catabolism and Anabolism in Acetogenic Bacteria Growing on Different Substrates

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