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Methanogen

About: Methanogen is a research topic. Over the lifetime, 1146 publications have been published within this topic receiving 48254 citations.


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Journal ArticleDOI
TL;DR: Methanogen populations of an intertidal mudflat in the Yangtze River estuary of China were investigated using 454-pyrosequencing and quantitative real-time polymerase chain reaction (qPCR), and current data indicate that Methanosarcinales and Methanomicrobiales are the most dominant methanogens within the entire depth profile down to 100 cm.
Abstract: Methanogen populations of an intertidal mudflat in the Yangtze River estuary of China were investigated based on the methyl coenzyme M reductase A (mcrA) gene using 454-pyrosequencing and quantitative real-time polymerase chain reaction (qPCR). Samples were collected at six depths from three locations. In the qPCR analyses, a mean depth-wise change of mcrA gene abundance was observed from (1.23 ± 0.13)×107 to (1.16 ± 0.29)×108 per g dried soil, which was inversely correlated with the depletion of sulfate (R2 =0.74; α = 0.05) and salinity (R2 = 0.66; α = 0.05). The copy numbers of mcrA was at least 1 order of magnitude higher than dissimilatory sulfate reductase B (dsrB) genes, likely indicating the importance of methanogenesis at the mudflat. Sequences related to the orders Methanomicrobiales, Methanosarcinales, Methanobacteriales, Methanococcales and the uncultured methanogens; Rice Cluster I (RC-I), Zoige cluster I (ZC-I) and anaerobic methane oxidizing archaeal lineage-1 (ANME-1) were detected. Methanomicrobiales and Methanosarcinales dominated the entire sediment layers, but detectable changes of proportions were observed with depth. The hydrogenotrophic methanogens Methanomicrobiales slightly increased with depth while Methanosarcinales showed the reverse. Chao1 and ACE richness estimators revealed higher diversity of methanogens near the surface (0–10 cm) when compared with the bottom sediments. The near-surface sediments were mainly dominated by the family Methanosarcinaceae (45 %), which has members that can utilize substrates that cannot be used by sulfate-reducing bacteria. Overall, current data indicate that Methanosarcinales and Methanomicrobiales are the most dominant methanogens within the entire depth profile down to 100 cm, with higher abundance and diversity of methanogens in the deeper and upper sediment layers, respectively.

48 citations

Journal ArticleDOI
TL;DR: In contrast to constant community structure, the transcription of functional mcrA genes strongly responded to O2 stress and the presence of inhibitor CH3 F, and the response patterns reflected the genomic and physiological traits of individual methanogens.
Abstract: Methane production in paddy soil is substantially suppressed after even a brief exposure of soil to oxygen. We hypothesized that the strong response of methanogen activity is reflected in the transcription of functional genes rather than in the composition of the community of methanogens. Therefore, we determined the community composition and the transcriptional response of methanogens in a rice field soil by targeting the mcrA gene (encoding the α subunit of methyl-coenzyme M reductase). Transcription of mcrA genes measured by quantitative PCR decreased by an order of magnitude after brief exposure to O2 . Terminal restriction fragment length polymorphism of mcrA genes and gene transcripts showed that although the community structure of methanogens did not change, the composition of transcripts dramatically responded to O2 exposure. In the beginning, transcripts of Methanocellales were the relatively most abundant, indicating resistance of these hydrogenotrophic methanogens against O2 stress. Later on, mcrA transcripts of acetoclastic methanogens became relatively more abundant coinciding with the turnover of acetate. The transcription of Methanosarcinaceae was relatively greater when acetate accumulated while Methanosaetaceae became more active when acetate concentrations decreased. In the presence of methyl fluoride, a specific inhibitor of acetoclastic methanogenesis, mcrA transcription by Methanosaetaceae was greatly suppressed while that of Methanosarcinaceae was less affected. Our study showed that in contrast to constant community structure as revealed by DNA-based fingerprinting the transcription of functional mcrA genes strongly responded to O2 stress and the presence of inhibitor CH3 F. The response patterns reflected the genomic and physiological traits of individual methanogens.

47 citations

Journal ArticleDOI
TL;DR: In this paper, an unstructured mathematical model was used to compare the influence of hydrogen transport and metabolic properties on mesophilic and hyperthermophilic cocultures.
Abstract: Interactions involving hydrogen transfer were studied in a coculture of two hyperthermophilic microorganisms: Thermotoga maritima, an anaerobic heterotroph, and Methanococcus jannaschii, a hydrogenotrophic methanogen. Cell densities of T. maritima increased 10-fold when cocultured with M. jannaschii at 85 degrees C, and the methanogen was able to grow in the absence of externally supplied H(2) and CO(2). The coculture could not be established if the two organisms were physically separated by a dialysis membrane, suggesting the importance of spatial proximity. The significance of spatial proximity was also supported by cell cytometry, where the methanogen was only found in cell sorts at or above 4.5 microm in samples of the coculture in exponential phase. An unstructured mathematical model was used to compare the influence of hydrogen transport and metabolic properties on mesophilic and hyperthermophilic cocultures. Calculations suggest the increases in methanogenesis rates with temperature result from greater interactions between the methanogenic and fermentative organisms, as evidenced by the sharp decline in H(2) concentration in the proximity of a hyperthermophilic methanogen. The experimental and modeling results presented here illustrate the need to consider the interactions within hyperthermophilic consortia when choosing isolation strategies and evaluating biotransformations at elevated temperatures.

47 citations

Journal ArticleDOI
TL;DR: In this article, the hydrogen isotope ratio of CH4 produced during rapid growth of the thermophilic methanogen Methanothermococcus okinawensis under high pH2 conditions was affected by the isotopic composition of H2, as concluded in a previous study of Methanothermobacter thermautotrophicus.
Abstract: Hydrogen and carbon isotope systematics of H2O–H2–CO2–CH4 in hydrogenotrophic methanogenesis and their relation to H2 availability were investigated. Two H2-syntrophic cocultures of fermentatively hydrogenogenic bacteria and hydrogenotrophic methanogens under conditions of <102 Pa-H2 and two pure cultures of hydrogenotrophic methanogens under conditions of ~105 Pa-H2 were tested. Carbon isotope fractionation between CH4 and CO2 during hydrogenotrophic methanogenesis was correlated with pH2, as indicated in previous studies. The hydrogen isotope ratio of CH4 produced during rapid growth of the thermophilic methanogen Methanothermococcus okinawensis under high pH2 conditions (~105 Pa) was affected by the isotopic composition of H2, as concluded in a previous study of Methanothermobacter thermautotrophicus. This “ $$ {\updelta \mathrm{D}}_{{\mathrm{H}}_2} $$ effect” is a possible cause of the diversity of previously reported values for hydrogen isotope fractionation between CH4 and H2O examined in H2-enriched culture experiments. Hydrogen isotope fractionation between CH4 and H2O, defined by (1000 + $$ {\updelta \mathrm{D}}_{{\mathrm{CH}}_4} $$ )/(1000 + $$ {\updelta \mathrm{D}}_{{\mathrm{H}}_2\mathrm{O}} $$ ), during hydrogenotrophic methanogenesis of the H2-syntrophic cocultures was in the range 0.67–0.69. The hydrogen isotope fractionation of our H2-syntrophic dataset overlaps with those obtained not only from low-pH2 experiments reported so far but also from natural samples of “young” methane reservoirs (0.66–0.74). Conversely, such hydrogen isotope fractionation is not consistent with that of “aged” methane in geological samples (≥0.79), which has been regarded as methane produced via hydrogenotrophic methanogenesis from the carbon isotope fractionation. As a possible process inducing the inconsistency in hydrogen isotope signatures between experiments and geological samples, we hypothesize that the hydrogen isotope signature of CH4 imprinted at the time of methanogenesis, as in the experiments and natural young methane, may be altered by diagenetic hydrogen isotope exchange between extracellular CH4 and H2O through reversible reactions of the microbial methanogenic pathway in methanogenic region and/or geological methane reservoirs.

47 citations

Journal ArticleDOI
TL;DR: M. methylutens, a methylotrophic methanogen isolated from submarine sediments, is suggested to be a new strain ofMethanococcoides methylutENS, an anaerobic methanogenic bacterium isolated from oxygenated coastal waters.
Abstract: Enrichment cultures containing marine plankton from oxygenated coastal waters (50–108% saturated) with supersaturated levels of methane (>700% saturated) yielded a strictly anaerobic methanogenic bacterium. Nonmotile, non-spore-forming, regular to slightly irregular cocci (0.5–0.8µm) were evident by phase contrast, epifluorescence, and scanning electron microscopies. The unpurified isolate required NaCl for growth, with maximal methanogenesis at 240 mM NaCl at 22°C. The optimal temperature range for growth was 22–31°C, and the optimal range for methanogenesis was 26–35°C. Mono-, di-, and trimethylated amines or methanol were substrates for methanogenesis; sodium acetate and H2:CO2 were not. The DNA base composition was 42 ±1% guanine plus cytosine. Serology suggested the isolate may be a new strain ofMethanococcoides methylutens. Morphology, growth physiology, DNA base content, and serology are all consistent with the type description ofM. methylutens, a methylotrophic methanogen isolated from submarine sediments.

47 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202379
2022139
202189
202067
201974
201863