scholarly journals Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments

2011 ◽  
Vol 8 (3) ◽  
pp. 795-814 ◽  
Author(s):  
R. Conrad ◽  
M. Noll ◽  
P. Claus ◽  
M. Klose ◽  
W. R. Bastos ◽  
...  
Keyword(s):  
Organic Matter ◽  
Lake Sediments ◽  
Carbon Isotope ◽  
Community Composition ◽  
Isotope Fractionation ◽  
Microbial Community Composition ◽  
Methanogenic Archaea ◽  
Methane Formation ◽  
Large Variability ◽  
Ch4 Production

Abstract. Methane is an important end product of degradation of organic matter in anoxic lake sediments. Methane is mainly produced by either reduction of CO2 or cleavage of acetate involving different methanogenic archaea. The contribution of the different methanogenic paths and of the diverse bacteria and archaea involved in CH4 production exhibits a large variability that is not well understood. Lakes in tropical areas, e.g. in Brazil, are wetlands with high potential impact on the global CH4 budget. However, they have hardly been studied with respect to methanogenesis. Therefore, we used samples from 16 different lake sediments in the Pantanal and Amazon region of Brazil to measure production of CH4, CO2, analyze the content of 13C in the products and in intermediately formed acetate, determine the abundance of bacterial and archaeal microorgansisms and their community composition and diversity by targeting the genes of bacterial and archaeal ribosomal RNA and of methyl coenzyme M reductase, the key enzyme of methanogenic archaea. These experiments were done in the presence and absence of methyl fluoride, an inhibitor of acetoclastic methanogenesis. While production rates of CH4 and CO2 were correlated to the content of organic matter and the abundance of archaea in the sediment, values of 13C in acetate, CO2, and CH4 were related to the 13C content of organic matter and to the path of CH4 production with its intrinsic carbon isotope fractionation. Isotope fractionation was small (average 10‰) for conversion of Corg to acetate-methyl, which was hardly further fractionated during CH4 production. However, fractionation was strong for CO2 conversion to CH4 (average 75‰), which generally accounted for >50% of total CH4 production. Canonical correspondence analysis did not reveal an effect of microbial community composition, despite the fact that it exhibited a pronounced variability among the different sediments.

scholarly journals Stable carbon isotope discrimination and microbiology of methane formation in tropical anoxic lake sediments

2010 ◽  
Vol 7 (6) ◽  
pp. 8619-8661 ◽  
Author(s):  
R. Conrad ◽  
M. Noll ◽  
P. Claus ◽  
M. Klose ◽  
W. R. Bastos ◽  
...  
Keyword(s):  
Organic Matter ◽  
Lake Sediments ◽  
Carbon Isotope ◽  
Community Composition ◽  
Isotope Fractionation ◽  
Microbial Community Composition ◽  
Methanogenic Archaea ◽  
Methane Formation ◽  
Large Variability ◽  
Ch4 Production

Abstract. Methane is an important end product of degradation of organic matter in anoxic lake sediments. Methane is mainly produced by either reduction of CO2 or cleavage of acetate involving different methanogenic archaea. The contribution of the different methanogenic paths and of the diverse bacteria and archaea involved in CH4 production exhibits a large variability that is not well understood. Lakes in tropical areas, e.g. in Brazil, are wetlands with high potential impact on the global CH4 budget. However, they have hardly been studied with respect to methanogenesis. Therefore, we used samples from 16 different lake sediments in the Pantanal and Amazon region of Brazil to measure production of CH4, CO2, analyze the content of 13C in the products and in intermediately formed acetate, determine the abundance of bacterial and archaeal microorgansisms and their community composition and diversity by targeting the genes of bacterial and archaeal ribosomal RNA and of methyl coenzyme M reductase, the key enzyme of methanogenic archaea. These experiments were done in the presence and absence of methyl fluoride, an inhibitor of acetoclastic methanogenesis. While production rates of CH4 and CO2 were correlated to the content of organic matter and the abundance of archaea in the sediment, values of 13C in acetate and CH4 were related to the 13C content of organic matter and to the path of CH4 production with its intrinsic carbon isotope fractionation. Isotope fractionation was small (average 10‰) for conversion of Corg to acetate-methyl, which was hardly further fractionated during CH4 production. However, fractionation was strong for CO2 conversion to CH4 (average 75‰), which generally accounted for >50% of total CH4 production. Canonical correspondence analysis did not reveal an effect of microbial community composition, despite the fact that it exhibited a pronounced variability among the different sediments.

scholarly journals Rumen microbial community composition varies with diet and host, but a core microbiome is found across a wide geographical range

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Gemma Henderson ◽  
◽  
Faith Cox ◽  
Siva Ganesh ◽  
Arjan Jonker ◽  
...  
Keyword(s):  
Microbial Community ◽  
Community Composition ◽  
Microbial Community Composition ◽  
Methanogenic Archaea ◽  
Methane Formation ◽  
Core Microbiome ◽  
Rumen Microbes ◽  
Metabolic Interactions ◽  
Occurrence Patterns ◽  
Dominant Bacteria

Abstract Ruminant livestock are important sources of human food and global greenhouse gas emissions. Feed degradation and methane formation by ruminants rely on metabolic interactions between rumen microbes and affect ruminant productivity. Rumen and camelid foregut microbial community composition was determined in 742 samples from 32 animal species and 35 countries, to estimate if this was influenced by diet, host species, or geography. Similar bacteria and archaea dominated in nearly all samples, while protozoal communities were more variable. The dominant bacteria are poorly characterised, but the methanogenic archaea are better known and highly conserved across the world. This universality and limited diversity could make it possible to mitigate methane emissions by developing strategies that target the few dominant methanogens. Differences in microbial community compositions were predominantly attributable to diet, with the host being less influential. There were few strong co-occurrence patterns between microbes, suggesting that major metabolic interactions are non-selective rather than specific.

δ13C of organic matter transported from the leaves to the roots in Eucalyptus delegatensis: short-term variations and relation to respired CO2

2007 ◽  
Vol 34 (8) ◽  
pp. 692 ◽  
Author(s):  
Arthur Gessler ◽  
Claudia Keitel ◽  
Naomi Kodama ◽  
Christopher Weston ◽  
Anthony J. Winters ◽  
...  
Keyword(s):  
Organic Matter ◽  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Stable Carbon Isotope ◽  
Water Soluble ◽  
Starch Accumulation ◽  
Diel Variation ◽  
Phloem Exudate ◽  
Carbon Isotope Fractionation ◽  
Eucalyptus Delegatensis

Post-photosynthetic carbon isotope fractionation might alter the isotopic signal imprinted on organic matter (OM) during primary carbon fixation by Rubisco. To characterise the influence of post-photosynthetic processes, we investigated the effect of starch storage and remobilisation on the stable carbon isotope signature (δ13C) of different carbon pools in the Eucalyptus delegatensis R. T. Baker leaf and the potential carbon isotope fractionation associated with phloem transport and respiration. Twig phloem exudate and leaf water-soluble OM showed diel variations in δ13C of up to 2.5 and 2‰, respectively, with 13C enrichment during the night and depletion during the day. Damped diel variation was also evident in bulk lipids of the leaf and in the leaf wax fraction. δ13C of nocturnal phloem exudate OM corresponded with the δ13C of carbon released from starch. There was no change in δ13C of phloem carbon along the trunk. CO2 emitted from trunks and roots was 13C enriched compared with the potential organic substrate, and depleted compared with soil-emitted CO2. The results are consistent with transitory starch accumulation and remobilisation governing the diel rhythm of δ13C in phloem-transported OM and fragmentation fractionation occurring during respiration. When using δ13C of OM or CO2 for assessing ecosystem processes or plant reactions towards environmental constraints, post-photosynthetic discrimination should be considered.

Organic matter additions to soil and effects on microbially mediated carbon cycling

2020 ◽  
Author(s):  
Rachel hasler ◽  
Mark pawlett ◽  
Jim harris ◽  
Helen bostock ◽  
Marc redmile-gordon
Keyword(s):  
Organic Matter ◽  
Microbial Community ◽  
Carbon Cycling ◽  
Community Composition ◽  
Soil Microbial Community ◽  
Microbial Community Composition ◽  
Soil Microbial ◽  
Horse Manure ◽  
Soil Microbial Community Composition

<p>The type of soil organic amendment selected can have profound implications for carbon cycling processes in soils. Understanding the link between this choice and its effect on the soil microbiome will improve our understanding of the capacity of these materials to improve carbon sequestration and cycling dynamics. Understanding and facilitating the lifestyle strategies of microorganisms processing organic matter is essential to improving our understanding of the terrestrial carbon cycle. This research focuses on utilising organic amendments to alter the indigenous soil microbial community composition and function to improve the capacity of the soil to cycle and store carbon in horticultural soils.  The effects of annual application of various organic fertilisers (peat, bracken, bark, horse manure, garden compost) in a long-term (10year) field experiment were explored. Sampling was completed pre and post application of organic matter within one season (following 10 years of applications) to identify which organic amendment was more effective in producing benefits to plants through improved soil organic matter and which amendments provide the greatest legacy effect on carbon cycling. The response of the soil microbial community composition (phospholipid fatty acid analysis) and carbon functional cycling dynamics (respiration using MicroResp™) were determined with a view to improving our understanding of the interaction between the materials applied and microbial processes. PCA of the MicroResp™ data identified that all treatments had a different functional profile compared to the control[PM1]  with peat being significantly different from all other treatments. Horse manure and bark differed significantly within a single growing season; prior and post organic matter addition in spring 2019.  Microbial biomass measurements for garden compost and horse manure were significantly higher following organic matter addition compared to all other treatments and the control[PM2] .  All treatments had a significant effect [PM3] on hot water extractable carbon and total carbon. Peat had a significantly different effect[PM4] , when compared to other treatments, on the soil PLFA profile and bark application significantly increased [PM5] the neutral lipid (NLFA) biomarker 16:1ω5.  Bark and horse manure application both significantly increased PLFA fungal biomarker 18:2ω6,9. No significant differences were found between the fungal/bacterial ratios of the organic matter additions prior to being added to the soil. These findings show that altering the resources available to the soil microbial community has a significant impact on soil microbial community composition and microbially mediated carbon cycling functionality. Increasing our understanding of how soil functions are altered by land management decisions will enable better informed predictions of the long-term benefits of organic matter applications on carbon sequestration and cycling dynamics.</p>

scholarly journals Stable Carbon Isotope Fractionation by Methylotrophic Methanogenic Archaea

2012 ◽  
Vol 78 (21) ◽  
pp. 7596-7602 ◽  
Author(s):  
Jörn Penger ◽  
Ralf Conrad ◽  
Martin Blaser
Keyword(s):  
Carbon Isotope ◽  
Isotope Fractionation ◽  
Stable Carbon Isotope ◽  
Methanogenic Archaea ◽  
Methanosarcina Barkeri ◽  
Stable Carbon ◽  
Methyl Fluoride ◽  
Content Type ◽  
Carbon Isotope Fractionation ◽  
Stable Carbon Isotope Fractionation

ABSTRACTIn natural environments methane is usually produced by aceticlastic and hydrogenotrophic methanogenic archaea. However, some methanogens can use C1compounds such as methanol as the substrate. To determine the contributions of individual substrates to methane production, the stable-isotope values of the substrates and the released methane are often used. Additional information can be obtained by using selective inhibitors (e.g., methyl fluoride, a selective inhibitor of acetoclastic methanogenesis). We studied stable carbon isotope fractionation during the conversion of methanol to methane inMethanosarcina acetivorans,Methanosarcina barkeri, andMethanolobus zinderiand generally found large fractionation factors (−83‰ to −72‰). We further tested whether methyl fluoride impairs methylotrophic methanogenesis. Our experiments showed that even though a slight inhibition occurred, the carbon isotope fractionation was not affected. Therefore, the production of isotopically light methane observed in the presence of methyl fluoride may be due to the strong fractionation by methylotrophic methanogens and not only by hydrogenotrophic methanogens as previously assumed.

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