Stable carbon isotope fractionation between substrates and products of Methanosarcina barkeri

Londry, Kathleen L.; Dawson, K.; Grover, H.; Summons, Roger E.; Bradley, Alexander S.

doi:10.1016/j.orggeochem.2008.03.002

Cited by 117 publications

(130 citation statements)

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“…When grown on H 2 and CO 2 , the reported fractionation factors varied by 8‰ (6,31,43), whereas fractionation covers a range of 13‰ on acetate (4,6,33,43), 12‰ on trimethylamine (43,44), and 9‰ on methanol (6,43). These differences would again point to a strain-specific variability rather than to a phylogenetic trait.…”

Section: Discussionmentioning

confidence: 93%

Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H ₂ and CO ₂

Blaser

Dreisbach

Conrad

2013

Appl Environ Microbiol

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Acetogenic bacteria are able to grow autotrophically on hydrogen and carbon dioxide by using the acetyl coenzyme A (acetyl-CoA) pathway. Acetate is the end product of this reaction. In contrast to the fermentative route of acetate production, which shows almost no fractionation of carbon isotopes, the acetyl-CoA pathway has been reported to exhibit a preference for light carbon. In Acetobacterium woodii the isotope fractionation factor () for 13 C and 12 C has previously been reported to be ‫؍‬ ؊58.6‰. To investigate whether such a strong fractionation is a general feature of acetogenic bacteria, we measured the stable carbon isotope fractionation factor of 10 acetogenic strains grown on H 2 and CO 2 . The average fractionation factor was TIC ‫؍‬ ؊57.2‰ for utilization of total inorganic carbon and acetate ‫؍‬ ؊54.6‰ for the production of acetate. The strongest fractionation was found for Sporomusa sphaeroides ( TIC ‫؍‬ ؊68.3‰), the lowest fractionation for Morella thermoacetica ( TIC ‫؍‬ ؊38.2‰). To investigate the reproducibility of our measurements, we determined the fractionation factor of 21 biological replicates of Thermoanaerobacter kivui. In general, our study confirmed the strong fractionation of stable carbon during chemolithotrophic acetate formation in acetogenic bacteria. However, the specific characteristics of the bacterial strain, as well as the cultural conditions, may have a moderate influence on the overall fractionation.A cetate is a central intermediate in the anaerobic degradation of organic matter and originates either from fermentation of organic compounds or from reduction of CO 2 with H 2 via the acetyl coenzyme A (acetyl-CoA) pathway (acetogenesis). The produced acetate serves as an important substrate for other microbes, e.g., for acetoclastic methanogens. The pathways involved in acetate turnover can be differentiated if the fractionation factors (ε) of the individual processes (e.g., fermentation, acetogenesis, and methanogenesis) are known (1). The fractionation factor can be quantified from the natural abundance of 13 C in acetate, organic carbon, inorganic carbon, and methane, which can all be measured in environmental samples.In anoxic environments and pure cultures of anaerobic microorganisms mainly the acetate degradation processes (methanogenesis and sulfate or sulfur reduction) have been investigated for the isotopic fractionation factors (2-10). The production of acetate, however, is less well characterized. In general it has been reported that fermentation exhibits only a weak (Ͻ5‰) fractionation (11-13). On the other hand, acetate production via chemolithotrophic acetogenesis fractionates stronger. However, it has thus far only been studied in Acetobacterium woodii (2). There a mean fractionation factor of ε ϭ Ϫ58.6‰ Ϯ 0.7‰ was reported, with both branches of the acetyl-CoA pathway contributing equally. Thus, the fractionation factor for total acetate (ε acetate total ϭ Ϫ57.3‰ Ϯ 2.3‰) was similar to that of the methyl group of acetate (ε methyl ϭ Ϫ58.2‰ Ϯ 3.1‰). These dat...

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Section: Discussionmentioning

confidence: 93%

Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H ₂ and CO ₂

Blaser

Dreisbach

Conrad

2013

Appl Environ Microbiol

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“…The substrates can be ordered based on the amount of fractionation that occurs. This ordering, from least to greatest fractionation (with fractionation factors indicated in parentheses), is as follows: acetate (1.01 to 1.03), dimethylsulfide (1.04 to 1.05), CO 2 /H 2 (1.03 to 1.08), trimethylamine (1.05 to 1.07), and methanol (1.07 to 1.09) (29,(37)(38)(39). The process of CO 2 reduction has been the most widely studied methane production pathway, encompassing both culture and environmental studies (29), which may explain why the widest range of fractionation factors is reported for this process.…”

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confidence: 99%

Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ ¹³ C Values of Methane Produced in Hypersaline Microbial Mats

Kelley

Nicholson

Beaudoin

et al. 2014

Appl Environ Microbiol

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bMethane production has been observed in a number of hypersaline environments, and it is generally thought that this methane is produced through the use of noncompetitive substrates, such as the methylamines, dimethylsulfide and methanol. Stable isotope measurements of the produced methane have also suggested that the methanogens are operating under conditions of substrate limitation. Here, substrate limitation in gypsum-hosted endoevaporite and soft-mat hypersaline environments was investigated by the addition of trimethylamine, a noncompetitive substrate for methanogenesis, and dried microbial mat, a source of natural organic matter. The ␦ 13 C values of the methane produced after amendments were compared to those in unamended control vials. At all hypersaline sites investigated, the ␦ 13 C values of the methane produced in the amended vials were statistically lower (by 10 to 71‰) than the unamended controls, supporting the hypothesis of substrate limitation at these sites. When substrates were added to the incubation vials, the methanogens within the vials fractionated carbon isotopes to a greater degree, resulting in the production of more 13 C-depleted methane. Trimethylamine-amended samples produced lower methane ␦ 13 C values than the mat-amended samples. This difference in the ␦ 13 C values between the two types of amendments could be due to differences in isotope fractionation associated with the dominant methane production pathway (or substrate used) within the vials, with trimethylamine being the main substrate used in the trimethylamine-amended vials. It is hypothesized that increased natural organic matter in the mat-amended vials would increase fermentation rates, leading to higher H 2 concentrations and increased CO 2 /H 2 methanogenesis.

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“…to day 17 (stationary phase) in Experiment 3, before the values stabilized (Figure 3), also suggests a substrate depletion effect (Fey et al, 2004;Goevert and Conrad, 2009;Londry et al, 2008;Whiticar, 1999). It is interesting to note that the stepped δ 13 C-CH 4 profile from the log phase to stationary phase was accompanied by a decrease in bacterial relative abundance that further supports the postulated substrate depletion effect ( Figure 3).…”

Section: Accepted M Manuscriptmentioning

confidence: 52%

“…In a closed system, such as a laboratory cultivation, substrate depletion may lead to more positive 13 C values. This occurs as the continued preferential consumption of the isotopically lighter molecules during methanogenesis leaves a residual pool of isotopically heavier carbon in the remaining substrate (Conrad et al, 2011;Londry et al, 2008;Valentine et al, 2004). In natural samples, substrate depletion effects have been postulated to have occurred where the δ 13 C-CH 4 of biogenic CH 4 showed a thermogenic signature but molecular compositions and carbon and hydrogen isotope fractionations indicated a biogenic origin (e.g., Golding et al, 2013;Hamilton et al, 2014).…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

“…Compared to molecular biological techniques that are time consuming and costly, stable isotope analysis of the produced CH 4 and CO 2 is cheaper and relatively easy to perform, and possibly more practical for process monitoring on an industrial scale. Isotope fractionation during methanogenesis has previously been investigated in laboratory samples using isolated microbes (Londry et al, 2008;Penger et al, 2012;Penning et al, 2006) and incubation experiments using environmental samples (Chidthaisong et al, 2002;Fey et al, 2004; A C C E P T E D M A N U S C R I P T…”

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confidence: 99%

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Carbon and hydrogen isotope fractionation during methanogenesis: A laboratory study using coal and formation water

Susilawati

Golding

Baublys

et al. 2016

International Journal of Coal Geology

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Carbon and hydrogen isotope compositions of CH 4 generated via methanogenesis in cultures of South Sumatra Basin (SSB) coalbed methane (CBM) formation waters grown on coal, acetate and H 2 +CO 2 were investigated. CH 4 production and molecular analysis confirmed the presence of active microbial communities that are able to convert coal into CH 4 using both acetoclastic and hydrogenotrophic pathways. The representative bacterial sequences were dominated by Bacteroidetes, Firmicutes and Deltaproteobacteria, while Methanosaeta and Methanosarcina were the most prevalent archaeal methanogens present in the cultures.CH 4 produced in this study's culturing experiments has δ 13 C values in the range of -50 ‰ to -20 ‰, with most values falling outside the current understanding of the carbon isotopic boundaries for biogenic CH 4 (-110 ‰ to -30 ‰). However, the corresponding apparent carbon isotopic α factor (α c = 1.02±0.006), and isotopic effect (ε c = -20.1 ‰ ±15.3) showed that CH 4 in SSB cultures was predominantly produced by acetoclastic methanogenesis, which is consistent with the results of molecular DNA analysis. In addition, the calculated contribution of CO 2 reduction from the δ 13 C values of coaltreated cultures was overall < 50 %, further confirming the high contribution of the acetoclastic pathway to CH 4 production in the SSB cultures. The outcome of this experimental study also suggests that δ 2 H-CH 4 values may not provide a reliable basis for distinguishing methanogenic pathways, while apparent carbon isotopic fractionation factor (α c ) and isotope effect (ε c ) are considered more useful indicators of the methanogenic pathway.The high δ 13 C-CH 4 values (>-30 ‰) and the dominance of Methanosaeta over Methanosarcina indicate that methanogens within the SSB cultures were operating at low substrate concentrations. An unusually positive δ 13 C-CH 4 suggests a substrate depletion effect, which is thought to be related to a decrease in the relative abundance of key bacterial coal degraders with formation water inoculum storage time. Closer observation of δ 13 C-CH 4 values during the growth of cultures within a single experiment also showed a 13 C-enrichment trend over time. At log phase of growth, the CH 4 produced was 13 C-depleted when compared to the stationary phase that also indicates substrate depletion effects. Finally, the δ 13 C-CH 4 values encountered in this study (as high as -20 ‰) highlight the possible positive extension of δ 13 C-CH 4 values of acetoclastic methanogenesis from those currently reported in the literature for natural and experimental samples (as high as -30 ‰).Keywords: Biogenic gas, coal, culture experiment, isotopic composition INTRODUCTIONArchaeal methanogens are the only known microorganisms capable of forming CH 4 . These strictly anaerobic microbes are restricted to utilizing simple compounds that contain no more than two carbon atoms. As such, complex organic compounds in anoxic environments (e.g., marine sediments, rice paddies, subsurface shales and coalbeds) ...

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Stable carbon isotope fractionation between substrates and products of Methanosarcina barkeri

Cited by 117 publications

References 33 publications

Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H ₂ and CO ₂

Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H ₂ and CO ₂

Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ ¹³ C Values of Methane Produced in Hypersaline Microbial Mats

Carbon and hydrogen isotope fractionation during methanogenesis: A laboratory study using coal and formation water

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Stable carbon isotope fractionation between substrates and products of Methanosarcina barkeri

Cited by 117 publications

References 33 publications

Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H 2 and CO 2

Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H 2 and CO 2

Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ 13 C Values of Methane Produced in Hypersaline Microbial Mats

Carbon and hydrogen isotope fractionation during methanogenesis: A laboratory study using coal and formation water

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Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H ₂ and CO ₂

Carbon Isotope Fractionation of 11 Acetogenic Strains Grown on H ₂ and CO ₂

Trimethylamine and Organic Matter Additions Reverse Substrate Limitation Effects on the δ ¹³ C Values of Methane Produced in Hypersaline Microbial Mats