ABSTRACT
Coalbed deposits are a unique subsurface environment and represent an underutilized resource for methane generation. Microbial communities extant in coalbed deposits are responsible for key subsurface biogeochemical cycling and could be utilized to enhance methane production in areas where existing gas wells have depleted methane stores, or in coalbeds that are unmined, or conversely be utilized for mitigation of methane release. Here we utilize metagenomics and metagenome-assembled genomes (MAGs) to identify extant microbial lineages and genome-resolved microbial metabolisms of coalbed produced water, which has not yet been explored in the Appalachian Basin (AppB). Our analyses resulted in the recovery of over 40 MAGs from 8 coalbed methane wells. The most commonly identified taxa among samples were hydrogenotrophic methanogens from the order Methanomicrobiales and these dominant MAGs were highly similar to one another. Conversely, low-abundance coalbed bacterial populations were taxonomically and functionally diverse, mostly belonging to a variety of Proteobacteria classes, and encoding various hydrocarbon solubilization and degradation pathways. The data presented herein provides novel insights into AppB coalbed microbial ecology, and our findings provide new perspectives on underrepresented Methanocalculus species and low-relative abundance bacterial assemblages in coalbed environments, and their potential roles in stimulation or mitigation of methane release.
Subject(s)
Metagenomics , Methanomicrobiales , Methanomicrobiales/metabolism , Metagenome , Hydrocarbons/metabolism , Methane/metabolism , BacteriaABSTRACT
A better understanding of the interaction between nanoplastics and archaea is crucial to fill the knowledge gaps regarding the ecological safety of nanoplastics. As a vital source for global methane emissions, methanogenic archaea have unique cell membranes that are distinctly different from those in all other forms of life, little is known about their interaction with nanoplastics. Here, we show that polystyrene nanoparticles functionalized with sulfonic acid (PS-SO3H) and amino (PS-NH2) interact with this methanogenic archaeon in distinct ways. Although both of them have no significant phenotype effects on Methanosarcina acetivorans C2A, these nanoparticles could affect DNA-mediated transposition of this methanogenic archaeon, and PS-SO3H also downregulated nitrogen fixation, nitrogen cycle metabolic process, oxidoreductase activity, etc. In addition, both nanoplastics decreased the protein contents in the extracellular polymer substances (EPS), with distinct binding sequences to the functional groups of the EPS. The single particle atomic force microscopy revealed that the force between the amino group and the M. acetivorans C2A was greater than that of sulfonic acid group. Our results exhibit that the surface groups of polystyrene nanoparticles control their risk on the methanogenic archaea, and these effects might influence their contribution on global methane emission.
Subject(s)
Methanosarcina , Nanoparticles , DNA/metabolism , Methane/metabolism , Methanomicrobiales/metabolism , Methanosarcina/genetics , Microplastics , Nitrogen/metabolism , Oxidoreductases , Polystyrenes , Sulfonic Acids/metabolismABSTRACT
An in vivo study was conducted to compare the enteric methane emissions and diversity of ruminal methanogens in cattle and buffaloes kept in the same environment and fed on the same diet. Six cattle and six buffaloes were fed on a similar diet comprising Napier (Pennisetum purpureum) green grass and concentrate in 70:30. After 90 days of feeding, the daily enteric methane emissions were quantified by using the SF6 technique and ruminal fluid samples from animals were collected for the diversity analysis. The daily enteric methane emissions were significantly greater in cattle as compared to buffaloes; however, methane yields were not different between the two species. Methanogens were ranked at different taxonomic levels against the Rumen and Intestinal Methanogen-Database. The archaeal communities in both host species were dominated by the phylum Euryarchaeota; however, Crenarchaeota represented <1% of the total archaea. Methanogens affiliated with Methanobacteriales were most prominent and their proportion did not differ between the two hosts. Methanomicrobiales and Methanomassillicoccales constituted the second largest group of methanogens in cattle and buffaloes, respectively. Methanocellales (Methanocella arvoryza) were exclusively detected in the buffaloes. At the species level, Methanobrevibacter gottschalkii had the highest abundance (55-57%) in both the host species. The relative abundance of Methanobrevibacter wolinii between the two hosts differed significantly. Methanosarcinales, the acetoclastic methanogens were significantly greater in cattle than the buffaloes. It is concluded that the ruminal methane yield in cattle and buffaloes fed on the same diet did not differ. With the diet used in this study, there was a limited influence (<3.5%) of the host on the structure of the ruminal archaea community at the species level. Therefore, the methane mitigation strategies developed in either of the hosts should be effective in the other. Further studies are warranted to reveal the conjunctive effect of diet and geographical locations with the host on ruminal archaea community composition.
Subject(s)
DNA, Archaeal/genetics , Diet/veterinary , Methane/metabolism , Methanomicrobiales/classification , Methanomicrobiales/isolation & purification , Rumen/metabolism , Animals , Buffaloes , Cattle , DNA, Archaeal/analysis , Male , Methane/analysis , Methanomicrobiales/genetics , Methanomicrobiales/metabolism , Rumen/microbiologyABSTRACT
The obstacle to optimal utilization of biogas technology is poor understanding of biogas microbiomes diversities over a wide geographical coverage. We performed random shotgun sequencing on twelve environmental samples. Randomized complete block design was utilized to assign the twelve treatments to four blocks, within eastern and central regions of Kenya. We obtained 42 million paired-end reads that were annotated against sixteen reference databases using two ENVO ontologies, prior to ß-diversity studies. We identified 37 phyla, 65 classes and 132 orders. Bacteria dominated and comprised 28 phyla, 42 classes and 92 orders, conveying substrate's versatility in the treatments. Though, Fungi and Archaea comprised 5 phyla, the Fungi were richer; suggesting the importance of hydrolysis and fermentation in biogas production. High ß-diversity within the taxa was largely linked to communities' metabolic capabilities. Clostridiales and Bacteroidales, the most prevalent guilds, metabolize organic macromolecules. The identified Cytophagales, Alteromonadales, Flavobacteriales, Fusobacteriales, Deferribacterales, Elusimicrobiales, Chlamydiales, Synergistales to mention but few, also catabolize macromolecules into smaller substrates to conserve energy. Furthermore, δ-Proteobacteria, Gloeobacteria and Clostridia affiliates syntrophically regulate PH2 and reduce metal to provide reducing equivalents. Methanomicrobiales and other Methanomicrobia species were the most prevalence Archaea, converting formate, CO2(g), acetate and methylated substrates into CH4(g). Thermococci, Thermoplasmata and Thermoprotei were among the sulfur and other metal reducing Archaea that contributed to redox balancing and other metabolism within treatments. Eukaryotes, mainly fungi were the least abundant guild, comprising largely Ascomycota and Basidiomycota species. Chytridiomycetes, Blastocladiomycetes and Mortierellomycetes were among the rare species, suggesting their metabolic and substrates limitations. Generally, we observed that environmental and treatment perturbations influenced communities' abundance, ß-diversity and reactor performance largely through stochastic effect. Understanding diversity of biogas microbiomes over wide environmental variables and its' productivity provided insights into better management strategies that ameliorate biochemical limitations to effective biogas production.
Subject(s)
Biofuels/microbiology , Metagenomics/methods , Microbiota/genetics , Archaea/genetics , Bacteria/genetics , Bacteria, Anaerobic/genetics , Bacteria, Anaerobic/metabolism , Biodiversity , Bioreactors/microbiology , Euryarchaeota/metabolism , Fermentation , Fungi/genetics , Kenya , Methane/metabolism , Methanomicrobiales/metabolism , Microbiota/physiology , Phylogeny , RNA, Ribosomal, 16SABSTRACT
Hydrogenotrophic methanogens produce CH4 using H2 as an electron donor to reduce CO2 In the absence of H2, many are able to use formate or alcohols as alternate electron donors. Methanogens from the order Methanomicrobiales are capable of growth with H2, but many lack genes encoding hydrogenases that are typically found in other hydrogenotrophic methanogens. In an effort to better understand electron flow in methanogens from the Methanomicrobiales, we undertook a genetic and biochemical study of heterodisulfide reductase (Hdr) in Methanoculleus thermophilus Hdr catalyzes an essential reaction by coupling the first and last steps of methanogenesis through flavin-based electron bifurcation. Hdr from M. thermophilus copurified with formate dehydrogenase (Fdh) and only displayed activity when formate was supplied as an electron donor. We found no evidence of an Hdr-associated hydrogenase, and H2 could not function as an electron donor, even with Hdr purified from cells grown on H2 We found that cells catalyze a formate hydrogenlyase activity that is likely essential for generating the formate needed for the Hdr reaction. Together, these results highlight the importance of formate as an electron donor for methanogenesis and suggest the ability to use formate is closely integrated into the methanogenic pathway in organisms from the order MethanomicrobialesIMPORTANCE Methanogens from the order Methanomicrobiales are thought to prefer H2 as an electron donor for growth. They are ubiquitous in anaerobic environments, such as in wastewater treatment facilities, anaerobic digesters, and the rumen, where they catalyze the terminal steps in the breakdown of organic matter. However, despite their importance, the metabolism of these organisms remains understudied. Using a genetic and biochemical approach, we show that formate metabolism is closely integrated into methanogenesis in Methanoculleus thermophilus This is due to a requirement for formate as the electron donor to heterodisulfide reductase (Hdr), an enzyme responsible for catalyzing essential reactions in methanogenesis by linking the initial CO2 fixing step to the exergonic terminal reaction of the pathway. These results suggest that hydrogen is not necessarily the preferred electron donor for all hydrogenotrophic methanogens and provide insight into the metabolism of methanogens from the order Methanomicrobiales.
Subject(s)
Formates/metabolism , Methanomicrobiales , Oxidoreductases , Methanomicrobiales/genetics , Methanomicrobiales/growth & development , Methanomicrobiales/metabolism , Oxidation-Reduction , Oxidoreductases/genetics , Oxidoreductases/metabolismABSTRACT
The applicability of a dynamic membrane (DM) was examined in the anaerobic treatment of high-strength food waste. A DM was established on woven polyester with a pore size of 50⯵m, which achieved a solids retention time to hydraulic retention time ratio of 2.1:12.1. The highest average rate of methane production (1.1 L CH4/L/d) was achieved with an organic loading rate (OLR) of 5.0â¯g chemical oxygen demand (COD)/L/d. Propionate was the most abundant volatile fatty acid (VFA) for OLRs above 3.1â¯g/L/d, but concentrations were maintained below 0.9â¯g/L. Up to 82% of the VFAs in the mixed liquor was reduced in the effluent, implying high methanogenic activity of the DM. Microbial assays confirmed a higher archaeal and bacterial content in the DM than in the mixed liquor at shear velocities above 1.0â¯cm/s. Methanolinea tarda, which is known to be propionate tolerant, was the predominant archaea in the DM.
Subject(s)
Bioreactors , Food , Microbiota , Anaerobiosis , Biological Oxygen Demand Analysis , Euryarchaeota/metabolism , Fatty Acids, Volatile/biosynthesis , Methane/biosynthesis , Methanomicrobiales/metabolismABSTRACT
In-situ upgrading of biogas in a mesophilic anaerobic digester of sewage sludge by sparging H2 through a membrane was studied. Large gas recirculation rates were required to facilitate H2 transfer to the bulk liquid phase; at â¯â¼200â¯Lâ¯Lreactor-1â¯d-1, H2 utilization efficiency averaged 94% and the specific CH4 production increased from 0.38â¯Lâ¯Lreactor-1â¯d-1, during conventional digestion, to 0.54â¯Lâ¯Lreactor-1â¯d-1. Sludge digestion was not compromised by elevated H2 partial pressure nor by the associated rise in the pH (8.1) because of CO2 removal. In this regard, VFA accumulation was not detected and the performance of VS removal was similar to the observed without H2 supply. Microbial analysis revealed that homoacetogens were outcompeted by hydrogenotrophic methanogens. Methanoculleus sp., Methanospirillum sp., Methanolinea sp. and Methanobacterium sp. were the hydrogenotrophic archaea present over the experiment.
Subject(s)
Biofuels , Hydrogen/metabolism , Sewage/microbiology , Anaerobiosis , Bioreactors/microbiology , Methanomicrobiales/metabolismABSTRACT
This study evaluated how tylosin (TYL), ciprofloxacin (CIP), and sulfadimidine (SM2) affected biogas and CH4 production during anaerobic digestion (AD) via their effects on the key genes related to methane production and the methanogenic community. The results showed that TYL, CIP, and SM2 reduced the production of methane during AD by 7.5%, 21.9%, and 16.0%, respectively. After AD for five days, CIP strongly inhibited the mcrA gene, where its abundance was 49% less than that in the control. TYL and SM2 decreased the abundances of Spirochaeta and Fibrobacteres during AD. High-throughput sequencing identified 10 methanogen genera, where Methanocorpusculum, Methanobrevibacter, and Methanosarcina accounted for 99.1% of the total archaeal reads. TYL and SM2 increased the efficiency of the acetoclastic methanogen pathway (Methanosarcina) by 29.04% and 52.79%, respectively. Redundancy analysis showed that Spirochaeta, Fibrobacteres, and Methanosarcina had positive correlations with CH4 and mcrA. We found that 30â¯mgâ¯kg-1 CIP had a strong inhibitory effect on methane production by influencing the abundances of Methanobrevibacter and Methanosarcina during AD.
Subject(s)
Ciprofloxacin/pharmacology , Manure/microbiology , Methane/biosynthesis , Methanomicrobiales/drug effects , Sulfamethazine/pharmacology , Tylosin/pharmacology , Anaerobiosis , Animals , Bioreactors/microbiology , Cattle , DNA Restriction Enzymes/genetics , Methane/metabolism , Methanomicrobiales/metabolism , Methanosarcinales/metabolismABSTRACT
Anaerobic sludge from a sewage treatment plant was used to acclimatize microbial colonies capable of anaerobic oxidation of methane (AOM) coupled to sulfate reduction. Clone libraries and fluorescence in situ hybridization were used to investigate the microbial population. Sulfate-reducing bacteria (SRB) (e.g., Desulfotomaculum arcticum and Desulfobulbus propionicus) and anaerobic methanotrophic archaea (ANME) (e.g., Methanosaeta sp. and Methanolinea sp.) coexisted in the enrichment. The archaeal and bacterial cells were randomly or evenly distributed throughout the consortia. Accompanied by sulfate reduction, methane was oxidized anaerobically by the consortia of methane-oxidizing archaea and SRB. Moreover, CH4 and SO42- were consumed by methanotrophs and sulfate reducers with CO2 and H2S as products. The H3CSH produced by methanotrophy was an intermediate product during the process. The methanotrophic enrichment was inoculated in a down-flow biofilter for the treatment of methane and H2S from a landfill site. On average, 93.33% of H2S and 10.71% of methane was successfully reduced in the biofilter. This study tries to provide effective method for the synergistic treatment of waste gas containing sulfur compounds and CH4.
Subject(s)
Hydrogen Sulfide/isolation & purification , Hydrogen Sulfide/metabolism , Methane/isolation & purification , Methane/metabolism , Anaerobiosis , Biodegradation, Environmental , Deltaproteobacteria/metabolism , Desulfotomaculum/metabolism , Methanomicrobiales/metabolism , Methanosarcinales/metabolism , Oxidation-ReductionABSTRACT
Exposure of a small amount of oxygen/air (microaeration) has been reported to benefit the anaerobic digestion (AD) process in enhancing hydrolysis, improving methane yield, stabilizing the process and scavenging hydrogen sulfide among others. The underlying mechanism of enhancing AD process via microaeration is the augmentation of activity and diversity of the microbial consortia that promotes syntrophic interactions among different microbial groups, thereby creating a more stable process. To design and implement a microaeration-based AD process, fundamental insights about the mechanism of the AD system at process, microbial and molecular levels must be fully explored. This review critically examines microaeration-based AD processes through our recent understandings of the effect of oxygen on microbial community structure, enzymatic, energetic, physiological, and biochemical aspects of the microbial-mediated process. Syntrophic interactions between hydrolytic, fermentative, sulfate reducing, syntrophic bacteria and methanogens under microaerobic conditions are examined to reveal putative mechanism and factors that need to be considered when implementing microaeration in AD process. Further studies are needed to better understand the microbial pathways and bioenergetics of the microaerobic AD process by adopting advanced molecular techniques such as metagenomics, transcriptomics, and proteomics.
Subject(s)
Bacteria/metabolism , Hydrogen Sulfide/metabolism , Methane/metabolism , Methanomicrobiales/metabolism , Microbial Consortia/physiology , Oxygen/metabolism , Anaerobiosis , Bioreactors , Fermentation , Gene Expression Profiling , Hydrolysis , Metabolic Networks and Pathways , Metagenomics , Oxidation-Reduction , ProteomicsABSTRACT
Permafrost thaw can bring negative consequences in terms of ecosystems, resulting in permafrost collapse, waterlogging, thermokarst lake development, and species composition changes. Little is known about how permafrost thaw influences microbial community shifts and their activities. Here, we show that the dominant archaeal community shifts from Methanomicrobiales to Methanosarcinales in response to the permafrost thaw, and the increase in methane emission is found to be associated with the methanogenic archaea, which rapidly bloom with nearly tenfold increase in total number. The mcrA gene clone libraries analyses indicate that Methanocellales/Rice Cluster I was predominant both in the original permafrost and in the thawed permafrost. However, only species belonging to Methanosarcinales showed higher transcriptional activities in the thawed permafrost, indicating a shift of methanogens from hydrogenotrophic to partly acetoclastic methane-generating metabolic processes. In addition, data also show the soil texture and features change as a result of microbial reproduction and activity induced by this permafrost thaw. Those data indicate that microbial ecology under warming permafrost has potential impacts on ecosystem and methane emissions.
Subject(s)
Greenhouse Effect , Methane/metabolism , Methanomicrobiales/metabolism , Methanosarcinales/metabolism , Permafrost/microbiology , Archaeal Proteins/genetics , Archaeal Proteins/metabolism , Methanomicrobiales/growth & development , Methanosarcinales/growth & development , MicrobiotaABSTRACT
The effect of chitosan on the development of granular sludge in upflow anaerobic sludge blanket reactors (UASB) when treating wastewater polluted with the organic solvents ethanol, ethyl acetate, and 1-ethoxy-2-propanol was evaluated. Three UASB reactors were operated for 219 days at ambient temperature with an organic loading rate (OLR) of between 0.3 kg COD m-3 d-1 and 20 kg COD m-3 d-1. One reactor was operated without the addition of chitosan, while the other two were operated with the addition of chitosan doses of 2.4 mg gVSS-1 two times. The three reactors were all able to treat the OLR tested with COD removal efficiencies greater than 90%. However, the time required to reach stable operation was considerably reduced in the chitosan-assisted reactors. The development of granules in the reactors with chitosan was accelerated and granules larger than 2000 µm were only observed in these reactors. In addition, these granules exhibited better physicochemical characteristics: the mean particle diameter (540 and 613 µm) was approximately two times greater than in the control reactor (300 µm), and the settling velocities exceeded 35 m h-1. The extracellular polymeric substances (EPS) in the reactors with the chitosan was found to be higher than in the control reactor. The protein-EPS content has been correlated with the granule size. The analyses of the microbial communities, performed through denaturing gradient gel electrophoresis and high-throughput sequencing, revealed that the syntrophic microorganisms belonging to genus Geobacter and the hydrogenotrophic methanogen Methanocorpusculum labreanum were predominant in the granules. Other methanogens like Methanosaeta species were found earlier in the chitosan-assisted reactors than in the control reactor.
Subject(s)
Bioreactors/microbiology , Chitosan , Solvents , Waste Disposal, Fluid/methods , Anaerobiosis , Biological Oxygen Demand Analysis , Geobacter/metabolism , Methanomicrobiales/metabolism , Microbiota/genetics , Microbiota/physiology , Particle Size , Polymers , Sewage , Waste Disposal, Fluid/instrumentation , Wastewater/chemistry , Water Pollutants, ChemicalABSTRACT
The red macroalga Asparagopsis taxiformis has been shown to significantly decrease methane production by rumen microbial communities. This has been attributed to the bioaccumulation of halogenated methane analogues produced as algal secondary metabolites. The objective of this study was to evaluate the impact of A. taxiformis supplementation on the relative abundance of methanogens and microbial community structure during in vitro batch fermentation. Addition of A. taxiformis (2% organic matter) or the halogenated methane analogue bromoform (5 µM) reduced methane production by over 99% compared to a basal substrate-only control. Quantitative PCR confirmed that the decrease in methane production was correlated with a decrease in the relative abundance of methanogens. High-throughput 16S ribosomal RNA gene amplicon sequencing showed that both treatments reduced the abundance of the three main orders of methanogens present in ruminants (Methanobacteriales, Methanomassiliicoccales and Methanomicrobiales). Shifts in bacterial community structure due to the addition of A. taxiformis and 5 µM bromoform were similar and concomitant with increases in hydrogen concentration in the headspace of the fermenters. With high potency and broad-spectrum activity against rumen methanogens, A. taxiformis represents a promising natural strategy for reducing enteric methane emissions from ruminant livestock.
Subject(s)
Methane/analogs & derivatives , Microbiota/drug effects , Rhodophyta/metabolism , Rumen/microbiology , Seaweed/metabolism , Animals , Bacteria/classification , Bacteria/drug effects , Bacteria/metabolism , DNA, Bacterial/genetics , Fermentation , Halogenation , Hydrogen/metabolism , In Vitro Techniques , Livestock/microbiology , Methane/metabolism , Methanobacteriales/drug effects , Methanobacteriales/metabolism , Methanomicrobiales/drug effects , Methanomicrobiales/metabolism , Microbiota/genetics , RNA, Ribosomal, 16S/genetics , Trihalomethanes/pharmacologyABSTRACT
Minerals that contain ferric iron, such as amorphous Fe(III) oxides (A), can inhibit methanogenesis by competitively accepting electrons. In contrast, ferric iron reduced products, such as magnetite (M), can function as electrical conductors to stimulate methanogenesis, however, the processes and effects of magnetite production and transformation in the methanogenic consortia are not yet known. Here we compare the effects on methanogenesis of amorphous Fe (III) oxides (A) and magnetite (M) with ethanol as the electron donor. RNA-based terminal restriction fragment length polymorphism with a clone library was used to analyse both bacterial and archaeal communities. Iron (III)-reducing bacteria including Geobacteraceae and methanogens such as Methanosarcina were enriched in iron oxide-supplemented enrichment cultures for two generations with ethanol as the electron donor. The enrichment cultures with A and non-Fe (N) dominated by the active bacteria belong to Veillonellaceae, and archaea belong to Methanoregulaceae and Methanobacteriaceae, Methanosarcinaceae (Methanosarcina mazei), respectively. While the enrichment cultures with M, dominated by the archaea belong to Methanosarcinaceae (Methanosarcina barkeri). The results also showed that methanogenesis was accelerated in the transferred cultures with ethanol as the electron donor during magnetite production from A reduction. Powder X-ray diffraction analysis indicated that magnetite was generated from microbial reduction of A and M was transformed into siderite and vivianite with ethanol as the electron donor. Our data showed the processes and effects of magnetite production and transformation in the methanogenic consortia, suggesting that significantly different effects of iron minerals on microbial methanogenesis in the iron-rich coastal riverine environment were present.
Subject(s)
Ferrosoferric Oxide/metabolism , Geologic Sediments/microbiology , Methane/metabolism , Methanomicrobiales/metabolism , Microbial Consortia/physiology , Rivers/microbiology , Anaerobiosis , Ferric Compounds/metabolism , Ferric Compounds/pharmacology , Geobacter/drug effects , Geobacter/metabolism , Iron/metabolism , Methanomicrobiales/drug effects , Methanosarcina/drug effects , Methanosarcina/metabolism , RNA, Ribosomal, 16S/geneticsABSTRACT
As many of the methanogens first encountered at hydrothermal vents were thermophilic to hyperthermophilic and comprised one of the lower roots of the evolutionary tree, it has been assumed that methanogenesis was one of the earliest, if not the earliest, pathway to life. It being well known that hydrothermal springs associated with serpentinization also bore abiotic methane, it had been further assumed that emergent biochemistry merely adopted and quickened this supposed serpentinization reaction. Yet, recent hydrothermal experiments simulating serpentinization have failed to generate methane so far, thus casting doubt on this assumption. The idea that the inverse view is worthy of debate, that is, that methanotrophy was the earlier, is stymied by the "fact" that methanotrophy itself has been termed "reverse methanogenesis," so allotting the methanogens the founding pedigree. Thus, attempting to suggest instead that methanogenesis might be termed reverse methanotrophy would require "unlearning"-a challenge to the subconscious! Here we re-examine the "impossibility" of methanotrophy predating methanogenesis as in what we have termed the "denitrifying methanotrophic acetogenic pathway." Advantages offered by such thinking are that methane would not only be a fuel but also a ready source of reduced carbon to combine with formate or carbon monoxide-available in hydrothermal fluids-to generate acetate, a target molecule of the first autotrophs. And the nitrate/nitrite required for the putative oxidation of methane with activated NO would also be a ready source of fixed nitrogen for amination reactions. Theoretical conditions for such a putative pathway would be met in a hydrothermal green rust-bearing exhalative pile and associated chimneys subject to proton and electron counter gradients. This hypothesis could be put to test in a high-pressure hydrothermal reaction chamber in which a cool carbonate/nitrate/nitrite-bearing early acidulous ocean simulant is juxtaposed across a precipitate membrane to an alkaline solution of hydrogen and methane. Key Words: Green rust-Methanotrophy-Nitrate reduction-Emergence of life. Astrobiology 17, 1053-1066.
Subject(s)
Exobiology/methods , Hydrothermal Vents/microbiology , Methane/biosynthesis , Methanomicrobiales/metabolism , Origin of Life , Carbon Monoxide/chemistry , Hydrogen/chemistry , Hydrothermal Vents/chemistry , Methane/chemistry , Nitrates/chemistry , Nitrites/chemistry , Oxidation-ReductionABSTRACT
AIMS: Pit mud is essential for the quality and yield of Chinese Luzhou-flavoured liquor. A reliable and fast method based on the use of microbial indicators combined with environmental factors coupled with metrology tools is needed to discriminate and classify different maturity levels of Luzhou-flavoured pit muds. METHODS AND RESULTS: Firmicutes, Bacteroidetes, Actinobacteria, Lactobacillus, Bacillus, Methanosarcina, Methanocorpusculum, Methanoculleus and Clostridium kluyveri were microbial indicators in Luzhou-flavoured pit muds. They were detected by real-time quantitative PCR. Environmental factors investigated included moisture content, pH, total acid and ammonia nitrogen. Principal component analysis (PCA) and partial least square-discriminant analysis were employed to explore the structure of the data and construct discrimination and classification models by reduction in the data dimensionality. Pit muds were distinguished and classified as new, trend to-be aged and aged. Moisture content and pH were significantly negatively correlated with new pit mud, while pH, total acid, amino nitrogen, Firmicutes, Bacteroidetes, Actinobacteria, Methanosarcina, Methanoculleus and C. kluyveri were significantly positively correlated with aged pit mud. CONCLUSIONS: Microbial indicators combined with environmental factors coupled to metrology tools can reliably and quickly discriminate and classify different maturity levels of Luzhou-flavoured pit muds. SIGNIFICANCE AND IMPACT OF THE STUDY: Modern techniques and metrology tools verified the correctness of the traditional sensory evaluation used in controlling the quality of pit mud, and will contribute to distinguishing different maturity levels of Chinese Luzhou-flavoured pit muds.
Subject(s)
Alcoholic Beverages/microbiology , Fermentation , Actinobacteria/genetics , Actinobacteria/isolation & purification , Actinobacteria/metabolism , Bacillus/genetics , Bacillus/isolation & purification , Bacillus/metabolism , Bacteroidetes/genetics , Bacteroidetes/isolation & purification , Bacteroidetes/metabolism , Firmicutes/genetics , Firmicutes/isolation & purification , Firmicutes/metabolism , Flavoring Agents , Humans , Hydrogen-Ion Concentration , Lactobacillus/genetics , Lactobacillus/isolation & purification , Lactobacillus/metabolism , Methanomicrobiaceae/genetics , Methanomicrobiaceae/isolation & purification , Methanomicrobiaceae/metabolism , Methanomicrobiales/genetics , Methanomicrobiales/isolation & purification , Methanomicrobiales/metabolism , Methanosarcina/genetics , Methanosarcina/isolation & purification , Methanosarcina/metabolism , TasteABSTRACT
Silage and dry are the two typical cornstalk forms. Either form could be used as substrate in biogas plants and might be replaced by another when shortage occurred. This study focused on the feeding sequence of these two kinds of feedstocks, aiming to discuss their specific methane potential (SMP). A 15-day hydraulic retention time was chosen for semi-continuous experiments based on the batch test results. In semi-continuous experiments, before and after feedstocks were exchanged, the significantly decreased and comparable SMPs of silage and dry cornstalks indicated that a basis of unstable digestion would result in incomplete methane release from the subsequent digestion. A higher similarity of bacterial community structure and greater quantity of bacteria were shown in acidified silage cornstalk digestion through band similarity analysis. Methanosaetaceae and methanomicrobiales were the predominant methanogens, and aceticlastic methanogenesis was the main route for methane production. The different feeding sequences affected the hydrolysis course and further influenced the methanogenic proliferation. Our work suggests that silage cornstalk digestion should be conducted before dry cornstalk digestion.
Subject(s)
Methane/metabolism , Methanomicrobiales/metabolism , Methanosarcinales/metabolism , Zea mays/metabolism , Anaerobiosis , Hydrolysis , Methane/biosynthesis , Methane/chemistry , Methanomicrobiales/chemistry , Methanosarcinales/chemistry , Silage , Substrate Specificity , Zea mays/chemistryABSTRACT
We have previously identified a sulfate methane transition zone (SMTZ) within the methane hydrate-bearing sediment in the Ulleung Basin, East Sea of Korea, and the presence of ANME-1b group in the sediment has been shown by phylogenetic analysis of a 16S rRNA gene. Herein, we describe taxonomic and functional profiling in the SMTZ sample by metagenomic analysis, comparing with that of surface sediment. Metagenomic sequences of 115 Mbp and 252 Mbp were obtained from SMTZ and surface sediments, respectively. The taxonomic profiling using BLASTX against the SEED within MG-RAST showed the prevalence of methanogens (19.1%), such as Methanosarcinales (12.0%) and Methanomicrobiales (4.1%) predominated within the SMTZ metagenome. A number of 185,200 SMTZ reads (38.9%) and 438,484 surface reads (62.5%) were assigned to functional categories, and methanogenesis-related reads were statistically significantly overrepresented in the SMTZ metagenome. However, the mapping analysis of metagenome reads to the reference genomes, most of the sequences of the SMTZ metagenome were mapped to ANME-1 draft genomes, rather than those of methanogens. Furthermore, the two copies of the methyl-coenzyme M reductase gene (mcrA) segments of the SMTZ metagenome were clustered with ANME-1b in the phylogenetic cluster. These results indicate that ANME-1b reads were miss-annotated to methanogens due to limitation of database. Many of key genes necessary for reverse methanogenesis were present in the SMTZ metagenome, except for N 5,N 10-methenyl-H4MPT reductase (mer) and CoB-CoM heterodisulfide reductase subunits D and E (hdrDE). These data suggest that the ANME-1b represents the primary player the anaerobic methane oxidation in the SMTZ, of the methane hydrate-bearing sediment at the Ulleung Basin, East Sea of Korea.
Subject(s)
Archaea/genetics , Euryarchaeota/genetics , Euryarchaeota/metabolism , Metagenome , Metagenomics , Methane/metabolism , Anaerobiosis , Archaea/classification , Archaea/isolation & purification , DNA, Archaeal/genetics , Euryarchaeota/classification , Euryarchaeota/isolation & purification , Geologic Sediments/microbiology , Methanomicrobiales/genetics , Methanomicrobiales/isolation & purification , Methanomicrobiales/metabolism , Methanosarcinales/genetics , Methanosarcinales/isolation & purification , Methanosarcinales/metabolism , Oceans and Seas , Oxidation-Reduction , Phylogeny , RNA, Ribosomal, 16S , Republic of KoreaABSTRACT
For evaluating the methanogenesis from typical methanogenic precursors (formate, acetate and H2/CO2), CH4 production kinetics were investigated at 37±1°C in batch anaerobic digestion tests and stimulated by modified Gompertz model. The results showed that maximum methanation rate from formate, acetate and H2/CO2 were 19.58±0.49, 42.65±1.17 and 314.64±3.58NmL/gVS/d in digested manure system and 6.53±0.31, 132.04±3.96 and 640.16±19.92NmL/gVS/d in sewage sludge system during second generation incubation. Meanwhile the model could not fit well in granular sludge system, while the rate of formate methanation was faster than from H2/CO2 and acetate. Considering both the kinetic results and microbial assay we could conclude that H2/CO2 methanation was the fastest methanogenic step in digested manure and sewage sludge system with Methanomicrobiales as dominant methanogens, while granular sludge with Methanobacteriales as dominant methanogens contributed to the fastest formate methanation.
Subject(s)
Acetates , Formates , Methane , Acetates/chemistry , Acetates/metabolism , Bioreactors/microbiology , Carbon Dioxide/chemistry , Carbon Dioxide/metabolism , Formates/chemistry , Formates/metabolism , Hydrogen/chemistry , Hydrogen/metabolism , Kinetics , Methane/analysis , Methane/chemistry , Methane/metabolism , Methanomicrobiales/chemistry , Methanomicrobiales/metabolism , Sewage/microbiologyABSTRACT
Nutrient addition as part of microbial enhanced oil recovery (MEOR) operations have important implications for more energy recovery from oil reservoirs, but very little is known about the in situ response of microorganisms after intervention. An analysis of two genes as biomarkers, mcrA encoding the key enzyme in methanogenesis and fthfs encoding the key enzyme in acetogenesis, was conducted during nutrient addition in oil reservoir. Clone library data showed that dominant mcrA sequences changed from acetoclastic (Methanosaetaceae) to CO2-reducing methanogens (Methanomicrobiales and Methanobacteriales), and the authentic acetogens affiliated to Firmicutes decreased after the intervention. Principal coordinates analysis (PCoA) and Jackknife environment clusters revealed evidence on the shift of the microbial community structure among the samples. Quantitative analysis of methanogens via qPCR showed that Methanobacteriales and Methanomicrobiales increased after nutrient addition, while acetoclastic methanogens (Methanosaetaceae) changed slightly. Nutrient treatment activated native CO2-reducing methanogens in oil reservoir. The high frequency of Methanobacteriales and Methanomicrobiales (CO2-reducers) after nutrient addition in this petroleum system suggested that CO2-reducing methanogenesis was involved in methane production. The nutrient addition could promote the methane production. The results will likely improve strategies of utilizing microorganisms in subsurface environments.