Showing papers on "Methanogen published in 2012"
TL;DR: The possibilities of Methanosarcina sp.
624 citations
TL;DR: In this article, the authors used quantitative polymerase chain reaction and terminal restriction fragment length polymorphism to determine the effects of these carbon additions on methanogen abundance and community composition.
Abstract: Summary
1. Sources of atmospheric CH4 are both naturally occurring and anthropogenic. In fact, some anthropogenic activities may influence the production of CH4 from natural sources, such as lakes.
2. Ongoing changes in the catchment of lakes, including eutrophication and increased terrestrial organic carbon export, may affect CH4 production rates as well as shape methanogen abundance and community structure. Therefore, inputs from catchments to lakes should be examined for their effects on CH4 production.
3. We added algal and terrestrial carbon separately to lake sediment cores and measured CH4 production. We also used quantitative polymerase chain reaction and terminal restriction fragment length polymorphism to determine the effects of these carbon additions on methanogen abundance and community composition.
4. Our results indicate that CH4 production rates were significantly elevated following the addition of algal biomass. Terrestrial carbon addition also appeared to increase methanogenesis rates; however, the observed increase was not statistically significant.
5. Interestingly, increased CH4 production rates resulted from increases in per-cell activity rather than an increase in methanogen abundance or community compositional shifts, as indicated by our molecular analyses.
6. Overall, anthropogenic impacts on aquatic ecosystems can influence methanogenesis rates and should be considered in models of global methane cycling and climate.
144 citations
TL;DR: It is found that intermittent drainage did not affect the growth of rice plants but significantly reduced the rates of both methane production and emission, and the composition of methanogenic community remained stable under dry/wet cycles, whereas that of metabolically active methanogens strongly changed.
Abstract: Intermittent drainage can substantially reduce methane emission from rice fields, but the microbial mechanisms remain poorly understood. In the present study, we determined the rates of methane production and emission, the dynamics of ferric iron and sulfate, and the abundance of methanogen mcrA genes (encoding the alpha subunit of methyl coenzyme M reductase) and their transcripts in response to alternate dry/wet cycles in paddy field soil. We found that intermittent drainage did not affect the growth of rice plants but significantly reduced the rates of both methane production and emission. The dry/wet cycles also resulted in shifts of soil redox conditions, increasing the concentrations of ferric iron and sulfate in the soil. Quantitative PCR analysis revealed that both mcrA gene copies and mcrA transcripts significantly decreased after dry/wet alternation compared to continuous flooding. Correlation and regression analyses showed that the abundance of mcrA genes and transcripts positively correlated with methane production potential and soil water content and negatively correlated with the concentrations of ferric iron and sulfate in the soil. However, the transcription of mcrA genes was reduced to a greater extent than the abundance of mcrA genes, resulting in very low mcrA transcript/gene ratios after intermittent drainage. Furthermore, terminal restriction fragment length polymorphism analysis revealed that the composition of methanogenic community remained stable under dry/wet cycles, whereas that of metabolically active methanogens strongly changed. Collectively, our study demonstrated a stronger effect of intermittent drainage on the abundance of mcrA transcripts than of mcrA genes in rice field soil.
137 citations
TL;DR: The results show that the absence of protozoa may affect differently the methanogen community and methane emissions in wethers.
Abstract: Understanding the interactions between hydrogen producers and consumers in the rumen ecosystem is important for ruminant production and methane mitigation. The present study explored the relationships between rumen protozoa, methanogens and fermentation characteristics. A total of six donor sheep harbouring (F, faunated) or not (D, defaunated) protozoa in their rumens (D animals were kept without protozoa for a period of a few months (D - ) or for more than 2 years (D+)) were used in in vitro and in vivo experiments. In vitro the absence of protozoa decreased NH3 and butyrate production and had no effect on methane. In contrast, the liquid-associated bacterial and methanogens fraction of D+ inocula produced more methane than D - and F inoculum (P < 0·05). In vivo fermentation parameters of donor animals showed the same trend on NH3 and butyrate and showed that D+ animals were high methane emitters, while D - were the lowest ( - 35 %). The concentration of dissolved dihydrogen measured after feeding followed the opposite trend. Methane emissions did not correlate with the relative abundance of methanogens in the rumen measured by quantitative PCR, but there was a trend for higher methanogens concentration in the solid-associated population of D+ animals compared with D - animals. In contrast, PCR-denaturing gradient gel electrophoresis profiles of methanogens' methyl coenzyme-M reductase A gene showed a clear clustering in liquid-associated fractions for all three groups of donors but fewer differences in solid-associated fractions. These results show that the absence of protozoa may affect differently the methanogen community and methane emissions in wethers.
132 citations
TL;DR: The draft genome sequence of "Candidatus Methanomethylophilus alvus" Mx1201, a methanogen present in the human gut, is reported, which contains genes needed for methylotrophic methanogenesis from methanol and tri-, di-, and monomethylamine.
Abstract: We report the draft genome sequence of "Candidatus Methanomethylophilus alvus" Mx1201, a methanogen present in the human gut. It was enriched from human feces under anaerobic conditions with methanol as the substrate. Its circular genome, of around 1.7 Mb, contains genes needed for methylotrophic methanogenesis from methanol and tri-, di-, and monomethylamine.
131 citations
TL;DR: Analysis of bioconversion of coal to methane in the San Juan Basin, New Mexico, suggests that coal methanogenesis is unlikely to be limited by methanogen biomass, but rather the activation and degradation of coal constituents.
129 citations
TL;DR: In this article, the authors investigated the coal bed methane (CBM) reservoir associated with Ordos Basin in China using 454 pyrosequencing reads and found that coal and coal samples were similar at the genus level, which were distinctly separated with water sample.
90 citations
TL;DR: A positive and significant correlation between the biogas production rate and methanogen abundance was observed and the applied method is suitable to describe microbiome into the anaerobic reactor, moreover methanogens concentration may have potential for use as a digestion optimisation tool.
87 citations
TL;DR: In this paper, the authors examined the biological conversion of CO2 to CH4 using hydrogenotrophic methanogens in a fixed bed reactor inoculated with anaerobic mixed culture from the anaerobacterial digestor of a sewage treatment plant.
Abstract: BACKGROUND: Biological conversion of CO2 to useful carbonic compounds such as methane is a potentially attractive technology for reducing its concentration in the atmosphere One of the advantages of this technology over chemical conversion is that it requires much lower energy for reduction of CO2 In this article, biological conversion of CO2 to CH4 using hydrogenotrophic methanogens was examined in a fixed bed reactor inoculated with anaerobic mixed culture from the anaerobic digestor of a sewage treatment plant
RESULTS: Methane formation commenced on the first day of operation of the fixed bed reactor CO2 fed to the reactor was reduced with H2 by hydrogenotrophic methanogens The feed ratio of CO2 to H2 is an important factor in determining the conversion rate of CO2 When the feed ratio is 4, methane is produced at the expected rate according to the chemical equation The CO2 conversion rate was 100% when the gas retention time was 38 h in the fixed bed reactor
CONCLUSIONS: The results show that the fixed bed reactor employing hydrogentrophic methanogens has the potential to be effective in converting CO2 to CH4 with a conversion rate of 100% at 38 h retention time Copyright © 2012 Society of Chemical Industry
87 citations
TL;DR: The result shows the applicability of marine macroalgae as biomass feedstock for the production of VFAs which can be converted to mixed alcohol fuels.
84 citations
TL;DR: This study demonstrates that the coexistence of two types of methanogens is necessary to respond successfully to perturbation and leads to stable process performance.
TL;DR: The results indicated that 16S rRNA levels of Methanomicrobiales and Methanosaetaceae in adhering sludge were higher than in deposited sludge, and they all contributed to the efficient performance of the fixed-bed reactor at low operating temperatures.
TL;DR: Nitrate may be used in achieving persistent mitigation of CH4 production by ruminants using in vitro ruminal cultures and adaptation of R. albus and R. flavefaciens seemed to adapt to nitrate, while F. succinogenes and methanogens did not.
TL;DR: The number of Methanosaeta organisms increased with increasing depth and was much higher than that of Methanosarcina organisms, suggesting that aceticlastic methanogens contribute to acetate metabolism to a greater extent than previously thought in marine environments, where sulfate-reducing acetate oxidation prevails.
Abstract: Among methanogens, only 2 genera, Methanosaeta and Methanosarcina, are known to contribute to methanogenesis from acetate, and Methanosaeta is a specialist that uses acetate specifically. However, Methanosaeta strains so far have mainly been isolated from anaerobic digesters, despite the fact that it is widespread, not only in anaerobic methanogenic reactors and freshwater environments, but also in marine environments, based upon extensive 16S rRNA gene-cloning analyses. In this study, we isolated an aceticlastic methanogen, designated strain 03d30q(T), from a tidal flat sediment. Phylogenetic analyses based on 16S rRNA and mcrA genes revealed that the isolate belongs to the genus Methanosaeta. Unlike the other known Methanosaeta species, this isolate grows at Na(+) concentrations of 0.20 to 0.80 M, with an optimum concentration of 0.28 M. Quantitative estimation using real-time PCR detected the 16S rRNA gene of the genus Methanosaeta in the marine sediment, and relative abundance ranged from 3.9% to 11.8% of the total archaeal 16S rRNA genes. In addition, the number of Methanosaeta organisms increased with increasing depth and was much higher than that of Methanosarcina organisms, suggesting that aceticlastic methanogens contribute to acetate metabolism to a greater extent than previously thought in marine environments, where sulfate-reducing acetate oxidation prevails. This is the first report on marine Methanosaeta species, and based on phylogenetic and characteristic studies, the name "Methanosaeta pelagica" sp. nov. is proposed for this novel species, with type strain 03d30q.
TL;DR: Tea saponins had a minor effect on the pattern of rumen fermentation and hence on nutrient digestion, and when added at 3 g/day in diets, TS could improve daily weight gain and feed efficiency in goats.
Abstract: Reducing methane emission from ruminant animals has implications not only for global environmental protection but also for efficient animal production. Tea saponins (TS) extracted from seeds, leaves or roots of tea plant are pentacyclic triterpenes. They have a lasting antiprotozoal effect, but little effect on the methanogen population in sheep. There was no significant correlation between the protozoa counts and methanogens. The TS decreased methanogen activity. It seems that TS influenced the activity of the methanogens indirectly via the depressed ciliate protozoal population. The TS addition decreased fungal population in the medium containing rumen liquor in in vitro fermentation, but no such effect was observed in the rumen liquor of sheep fed TS. Tea saponins had a minor effect on the pattern of rumen fermentation and hence on nutrient digestion. When added at 3 g/day in diets, TS could improve daily weight gain and feed efficiency in goats. No positive associative effect existed between TS and disodium fumarate or soybean oil on methane suppression. Inclusion of TS in diets may be an effective way for improving feed efficiency in ruminants.
TL;DR: Based upon the microbial community composition and the isotopic signature of methane associated with the Cook Inlet basin site, a simplified reaction network beginning with the breakdown of coal macromolecules, followed by fermentation and methylotrophic and acetoclastic methane production is proposed.
Abstract: Filter-collected production water samples from a methane-rich gas field in the Cook Inlet basin of Alaska were investigated using whole-cell rRNA-targeted fluorescence in situ hybridization (FISH) and 16S rRNA tag pyrosequencing. Both techniques were consistent in determining the microbial community composition, including the archaeal or bacterial dominance of samples. The archaeal community is dominated by the obligate methylotrophic methanogen genus Methanolobus as well as the nutritional generalist methanogen genus Methanosarcina, which is capable of utilizing acetate, CO2, and methyl-bearing compounds. The most-abundant bacterial groups are Firmicutes, notably of the Acetobacterium genus, and Cytophaga-Flexibacter-Bacteroides species (CFBs) affiliated with the order Bacteroidales. We observed spatial variation among samples in both the percentage of members of Archaea compared to that of members of Bacteria and the dominant members of the bacterial community, differences which could not be explained with the available geochemical data. Based upon the microbial community composition and the isotopic signature of methane associated with the Cook Inlet basin site, we propose a simplified reaction network beginning with the breakdown of coal macromolecules, followed by fermentation and methylotrophic and acetoclastic methane production.
TL;DR: This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible, and the fact that some 50% of the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction which should be valorized properly, for instance as slow release organic fertilizer.
Abstract: The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33°C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6–5.9 g biomass-COD L−1 day−1 with membrane fluxes ranging from 1 to 0.8 L m−2 h−1. The total COD recovered as biogas was in the order of 52%. The input suspension was converted to a clear effluent rich in total ammonium nitrogen (546 mg TAN L−1) and phosphate (141 mg PO4-P L−1) usable as liquid fertilizer. The microbial community richness, dynamics, and organization in the reactor were interpreted using the microbial resource management approach. The AnMBR communities were found to be moderate in species richness and low in dynamics and community organization relative to UASB and conventional CSTR sludges. Quantitative polymerase chain reaction analysis revealed that Methanosaeta sp. was the dominant acetoclastic methanogen species followed by Methanosarcina sp. This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible. The fact that some 50% of the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction which should be valorized properly, for instance as slow release organic fertilizer. Overall, 1 kg of algae dry matter (DM) could be valorized in the form of biogas (€2.07), N and P in the effluent (€0.02) and N and P in the digestate (€0.04), thus totaling about €2.13 per kilogram algae DM.
TL;DR: Two thermophilic archaea, strain PK and strain MG, were isolated from a culture enriched at 80°C from the inner surface material of a hot oil pipeline and the physiological characteristics of organisms both alone and in combination could conceivably contribute to pipeline corrosion.
Abstract: Summary Two thermophilic archaea, strain PK and strain MG, were isolated from a culture enriched at 80°C from the inner surface material of a hot oil pipeline. Strain PK could ferment complex organic nitrogen sources (e.g. yeast extract, peptone, tryptone) and was able to reduce elemental sulfur (S°), Fe 3+ and Mn 4+ . Phylogenetic analysis revealed that the organism belonged to the order Thermococcales. Incubations of this strain with elemental iron (Fe°) resulted in the abiotic formation of ferrous iron and the accumulation of volatile fatty acids during yeast extract fermentation. The other isolate, strain MG, was a H2:CO2-utilizing methanogen, phylogenetically affiliated with the genus Methanothermobacter family. Co-cultures of the strains grew as aggregates that produced CH4 without exogenous H2 amendment. The co-culture produced the same suite but greater concentrations of fatty acids from yeast extract than did strain PK alone. Thus, the physiological characteristics of organisms both alone and in combination could conceivably contribute to pipeline corrosion. The Thermococcus strain PK could reduce elemental sulfur to sulfide, produce fatty acids and reduce ferric iron. The hydrogenotrophic methanogen strain MG enhanced fatty acid production by fermentative organisms but could not couple the dissolution Fe° with the consumption of water-derived H2 like other methanogens.
TL;DR: The RFLP-based 16S rRNA gene-targeted phylogenetic analysis showed that clones were closely related to diverse group of methanogens comprising members of Methanomicrobi Families, Methanosarcinaceae, Methanosaetaceae and RC I.
TL;DR: A combined biogeochemical and molecular genetic study of creek sediments from Arne Peninsula salt-marsh determined the substrates used for methanogenesis and the distribution of the common methanogens, Methanosarcinales and Methanomicrobiales capable of metabolising these substrates, suggesting close relationship between the depth distribution of methanogenic substrate utilization and specific methanogen that can utilize these compounds.
Abstract: A combined biogeochemical and molecular genetic study of creek sediments (down to 65 cm depth) from Arne Peninsula salt-marsh (Dorset, UK) determined the substrates used for methanogenesis and the distribution of the common methanogens, Methanosarcinales and Methanomicrobiales capable of metabolising these substrates. Methane concentrations increased by 11 cm, despite pore water sulphate not being removed until 45 cm. Neither upward methane diffusion or anaerobic oxidation of methane seemed to be important in this zone. In the near-surface sulphate-reduction zone (5–25 cm) turnover time to methane for the non-competitive methanogenic substrate trimethylamine was most rapid (80 days), and were much longer for acetate (7900 days), methanol (40,500 days) and bicarbonate (361,600 days). Methylamine-utilizing Methanosarcinales were the dominant (60–95%) methanogens in this zone. In deeper sediments rates of methanogenesis from competitive substrates increased substantially, with acetate methanogenic rates becoming ∼100 times greater than H2/CO2 methanogenesis below 50 cm. In addition, there was a dramatic change in methanogen diversity with obligate acetate-utilizing, Methanosaeta related sequences being dominant. At a similar depth methanol turnover to methane increased to its most rapid (1700 days). This activity pattern is consistent with deeper methanogen populations (55 cm) being dominated by acetate-utilizing Methanosaeta with H2/CO2 and alcohol-utilizing Methanomicrobiales also present. Hence, there is close relationship between the depth distribution of methanogenic substrate utilization and specific methanogens that can utilize these compounds. It is unusual for acetate to be the dominant methanogenic substrate in coastal sediments and δ13C-CH4 values (−74 to −71‰) were atypical for acetate methanogenesis, suggesting that common stable isotope proxy models may not apply well in this type of dynamic anoxic sediment, with multiple methanogenic substrates.
TL;DR: Results suggested that past and ongoing biodegradation of coal by methylotrophic methanogens and syntrophic bacteria, as well as thermogenic CBM production, contributed to the Liulin CBM reserves associated with the Eastern Ordos Basin.
Abstract: To identify the methanogenic pathways present in a deep coal bed methane (CBM) reservoir associated with Eastern Ordos Basin in China, a series of geochemical and microbiological studies was performed using gas and water samples produced from the Liulin CBM reservoir. The composition and stable isotopic ratios of CBM implied a mixed biogenic and thermogenic origin of the methane. Archaeal 16S rRNA gene analysis revealed the dominance of the methylotrophic methanogen Methanolobus in the water produced. The high potential of methane production by methylotrophic methanogens was found in the enrichments using the water samples amended with methanol and incubated at 25 and 35 °C. Methylotrophic methanogens were the dominant archaea in both enrichments as shown by polymerase chain reaction (PCR)–denaturing gradient gel electrophoresis (DGGE). Bacterial 16S rRNA gene analysis revealed that fermentative, sulfate-reducing, and nitrate-reducing bacteria inhabiting the water produced were a factor in coal biodegradation to fuel methanogens. These results suggested that past and ongoing biodegradation of coal by methylotrophic methanogens and syntrophic bacteria, as well as thermogenic CBM production, contributed to the Liulin CBM reserves associated with the Eastern Ordos Basin.
TL;DR: The results showed that as in the Antarctic methanogen, Methanococcoides burtonii, genes for methanogenesis, biosynthesis and protein synthesis were all downregulated by the cold in R15, but the RNA polymerase complex was upregulated at cold, as well as a gene cluster for a putative exosome complex, suggesting that exosomal RNA decay may be cold-accelerated.
Abstract: We analysed the cold-responsive gene repertoire for a psychrophilic methanogen, Methanolobus psychrophilus R15 through genomic and RNA-seq assayed transcriptomic comparisons for cultures at 18°C (optimal temperature) versus 4°C. The differences found by RNA-seq analysis were verified using quantitative real time-PCR assay. The results showed that as in the Antarctic methanogen, Methanococcoides burtonii, genes for methanogenesis, biosynthesis and protein synthesis were all downregulated by the cold in R15. However, the RNA polymerase complex was upregulated at cold, as well as a gene cluster for a putative exosome complex, suggesting that exosome-mediated RNA decay may be cold-accelerated. Unexpectedly, the chaperonin genes for both thermosome and GroES/EL were all upregulated at 4°C. Strain R15 possessed eight protein families for oxygen detoxification, including both anaerobe-specific superoxide reductase (SOR) and the aerobe-typical superoxide dismutase (SOD)-catalase oxidant-removing system, implying the higher oxidative tolerance. Compared with a mesophilic methanogen, R15 survived in higher paraquat, a redox-cycling drug. Moreover, 71 one-component systems and 50 two-component systems for signal transduction ranked strain R15, together with M. burtonii, as being highly adaptive among archaea. Most of them exhibited cold-enhanced expression, indicating their involvement in cold adaptation. This study has added new perspectives on the cold adaptation of methanogenic archaea.
TL;DR: It is proposed that the dominant methanogen type in wetlands is primarily influenced by available DOC concentration, and the variation in CH4 production potential in the wetlands of eastern China is attributable to differences in the DOC content and the dominant type of methanogens present.
Abstract: Significant spatial variation in CH(4) emissions is a well-established feature of natural wetland ecosystems. To understand the key factors affecting CH(4) production, the variation in community structure of methanogenic archaea, in relation to substrate and external environmental influences, was investigated in selected wetlands across China, using denaturing gradient gel electrophoresis. Case study areas were the subtropical Poyang wetland, the warm-temperate Hongze wetland, the cold-temperate Sanjiang marshes, and the alpine Ruoergai peatland on the Qinghai-Tibetan Plateau. The topsoil layer in the Hongze wetland exhibited the highest population of methanogens; the lowest was found in the Poyang wetland. Maximum CH(4) production occurred in the topsoil layer of the Sanjiang Carex lasiocarpa marsh, the minimum was observed in the Ruoergai peatland. CH(4) production potential was significantly correlated with the dissolved organic carbon (DOC) concentration but not with the abundance or diversity indices of methanogenic archaea. Phylogenetic analysis and DOC concentration indicated a shift in the dominant methanogen from the hydrogenotrophic Methanobacteriales in DOC-rich wetlands to Methanosarcinaceae with a low affinity in wetlands with relatively high DOC and then to the acetotrophic methanogen Methanosaetaceae with a high affinity in wetlands with low DOC, or with high DOC but rich sulfate-reducing bacteria. Therefore, it is proposed that the dominant methanogen type in wetlands is primarily influenced by available DOC concentration. In turn, the variation in CH(4) production potential in the wetlands of eastern China is attributable to differences in the DOC content and the dominant type of methanogen present.
TL;DR: Results demonstrated that methane could exert anti-inflammatory effects in a dog small intestinal ischemia-reperfusion model, which seems to be good news in application of methane as a therapeutic gas.
Abstract: Background: Methane is an attractive fuel. Biologically, methanogens in the colon can use carbon dioxide and hydrogen to produce methane as a by-product. It was previously considered that methane is not utilized by humans. However, in a recent study, results demonstrated that methane could exert anti-inflammatory effects in a dog small intestinal ischemia-reperfusion model. Point of view: Actually, the bioactivity of methane has been investigated in gastrointestinal diseases, but the exact mechanism underlying the anti-inflammatory effects is required to be further elucidated. Methane can cross the membrane and is easy to collect due to its abundance in natural gas. Although methane is flammable, saline rich in methane can be prepared for clinical use. These seem to be good news in application of methane as a therapeutic gas. Conclusion: Several problems should be resolved before its wide application in clinical practice.
TL;DR: It is shown that five recently isolated Methanococcoides strains from a range of sediments can directly utilize choline for methanogenesis producing ethanolamine, giving them the advantage that they would not be reliant on bacterial syntrophs for their substrate supply.
Abstract: Choline (N,N,N-trimethylethanolamine), which is widely distributed in membrane lipids and is a component of sediment biota, has been shown to be utilized anaerobically by mixed prokaryotes cultures to produce methane, but not by pure cultures of methanogens. Here we show that five recently isolated Methanococcoides strains from a range of sediments (Aarhus Bay, Denmark; Severn Estuary mudflats at Portishead, UK; Darwin Mud Volcano, Gulf of Cadiz; Napoli mud volcano, Eastern Mediterranean) can directly utilise choline for methanogenesis producing ethanolamine, which is not further metabolised. Di- and monomethylethanolamine are metabolic intermediates that temporarily accumulate. Consistent with this dimethylethanolamine was shown to be another new growth substrate, but monomethylethanolamine was not. The specific methanogen inhibitor 2-bromoethanesulfonate (BES) inhibited methane production from choline. When choline and trimethylamine are provided together diauxic growth occurs, with trimethylamine being utilized first and then after a lag (∼7 days) choline is metabolised. Three type strains of Methanococcoides (M. methylutens, M. burtonii and M. alaskense), in contrast, did not utilize choline. However, two of them (M. methylutens and M. burtonii) did metabolise dimethylethanolamine. These results extend the known substrates that can be directly utilized by some methanogens, giving them the advantage that they would not be reliant on bacterial syntrophs for their substrate supply.
TL;DR: Syntrophic cellulose decomposition by the cellulolytic bacteria and hydrogenotrophic methanogens would be the dominant reaction in the thermophilic methanogenic reactor degrading cellulosic materials.
TL;DR: It is demonstrated that climate warming stimulates CH4 emission in a rice paddy by altering the abundance and activity of methanogenic archaea in the roots.
Abstract: Rice paddies are one of the most important sources of CH4 emission from the terrestrial ecosystem. A Free-air CO2 Enrichment (FACE) experiment, which included a soil warming treatment, was conducted in a rice paddy at Shizukuishi, Japan. In this study, the changes in CH4 emission from a rice paddy, caused by global climate change, were explored in relation to the structural changes that have occurred in the methanogenic archaeal communities found in the soil and roots. The composition of the archaeal community was examined by terminal restriction fragment length polymorphism (T-RFLP) using the 16S rRNA gene, while its abundance was measured by real-time PCR using the methyl coenzyme M reductase (mcrA) gene. The archaeal community in the roots showed considerable change, characterized by the dominance of hydrogenotrophic methanogens and a corresponding decrease in acetoclastic methanogens. Seasonal changes in CH4 flux were closely related to the changes in methanogen abundance in the roots. Elevated CO2 caused an increase in root mass, which increased the abundance of methanogens leading to a rise in CH4 emissions. However, soil warming stimulated CH4 emissions by increasing CH4 production per individual methanogen. These results demonstrated that climate warming stimulates CH4 emission in a rice paddy by altering the abundance and activity of methanogenic archaea in the roots.
TL;DR: Nitrogen enrichment to salt marsh sediments increases methane flux by stimulating the methanogen community, and methylotroph abundance and composition did not vary across the experimental nitrogen gradient in the field.
Abstract: Methane (CH4) flux from ecosystems is driven by C1-cycling microorganisms – the methanogens and the methylotrophs. Little is understood about what regulates these communities, complicating predictions about how global change drivers such as nitrogen enrichment will affect methane cycling. Using a nitrogen addition gradient experiment in three Southern California salt marshes, we show that sediment CH4 flux increased linearly with increasing nitrogen addition (1.23 µg CH4 m-2 d-1 for each g N m-2 yr-1 applied) after seven months of fertilization. To test the reason behind this increased CH4 flux, we conducted a microcosm experiment altering both nitrogen and carbon availability under aerobic and anaerobic conditions. Methanogenesis appeared to be both nitrogen and carbon (acetate) limited. N and C each increased methanogenesis by 18%, and together by 44%. In contrast, methanotrophy was stimulated by carbon (methane) addition (830%), but was unchanged by nitrogen addition. Sequence analysis of the sediment methylotroph community with the methanol dehydrogenase gene (mxaF) revealed three distinct clades that fall outside of known lineages. However, in agreement with the microcosm results, methylotroph abundance (assayed by qPCR) and composition (assayed by T-RFLP) did not vary across the experimental nitrogen gradient in the field. Together, these results suggest that nitrogen enrichment to salt marsh sediments increases methane flux by stimulating the methanogen community.
TL;DR: In this paper, experimental tests that were conducted to recover the energy embedded in these metabolites were conducted and the results showed that the second methanogenic stage increases the overall energy efficiency of the two-stage process to a great extent compared to the H 2 stage on its own.
TL;DR: The use of intact archaeol is proposed as a useful biomarker for methanogen biomass in soil and to track changes in moisture status and aeration related to climate change.
Abstract: Oxic soils typically are a sink for methane due to the presence of high-affinity methanotrophic Bacteria capable of oxidising methane. However, soils experiencing water saturation are able to host significant methanogenic archaeal communities, potentially affecting the capacity of the soil to act as a methane sink. In order to provide insight into methanogenic populations in such soils, the distribution of archaeol in free and conjugated forms was investigated as an indicator of fossilised and living methanogenic biomass using gas chromatography-mass spectrometry with selected ion monitoring. Of three soils studied, only one organic matter-rich site contained archaeol in quantifiable amounts. Assessment of the subsurface profile revealed a dominance of archaeol bound by glycosidic headgroups over phospholipids implying derivation from fossilised biomass. Moisture content, through control of organic carbon and anoxia, seemed to govern trends in methanogen biomass. Archaeol and crenarchaeol profiles differed, implying the former was not of thaumarcheotal origin. Based on these results, we propose the use of intact archaeol as a useful biomarker for methanogen biomass in soil and to track changes in moisture status and aeration related to climate change.