Methane (CH4) has attracted attention as not only synthetic natural gas, but also one of the hy-drogen carriers in terms of energy density. On the other hand, there exist bacterial ecosystems in nature that can decompose organic compounds to produce CH4 and CO2. In this study, Clostridi-um cellulovorans was first cultivated with pig manure (PM) as an unused biomass. Regarding the measurement of organic acids by high-performance liquid chromatography (HPLC), acetate and butyrate were increased in the C. cellulovorans medium containing 0.5% PM, while formate and lactate were decreased in it. Next, in comparison with carbon sources such as glucose, cellobiose, and acetate, cocultivation of C. cellulovorans and Methanosarcina mazei or microbial flora of me-thane production (MFMP) was performed in the C. cellulovorans medium. These results revealed that 0.5% acetate as the sole carbon source produced CH4 only by cocultivating C. cellulovorans and MFMP. Furthermore, MFMP was only cultivated with 1% acetate or 1% methane as a carbon source after precultivated with 0.5% glucose medium for 12 h. As a result, methane productivity of MFMP with 1% methanol medium was approximately eight times higher than that with 1% acetate medium. Finally, next-generation sequencing (NGS) analysis of MFMP after cultivation with 1% acetate or 1% methane was carried out. Interestingly, Methanofollis (0.211%) belonging to H2/CO2 -using methanogens (CO2 reduction pathway) was dominant in the 1% acetate medium for 72 h cultivation, whereas Methanosarcina siciliae (1.178%), M. barkeri (0.571%), and Methano-follis (0.490%) were major species in 1% methanol medium for 72 h cultivation. Since Methano-sarcina spp. are belonging to acetoclasts (acetoclastic pathway), methanol could promote to grow Methanosarcina spp. rather than acetate. Therefore, it seemed Methanosarcina spp. may play a key methanogenesis in MFMP. Thus, these results will provide important information for low cost biomethane production.

Methane (CH4) has attracted attention as not only synthetic natural gas, but also one of the hy-drogen carriers in terms of energy density. On the other hand, there exist bacterial ecosystems in nature that can decompose organic compounds to produce CH4 and CO2. In this study, Clostridi-um cellulovorans was first cultivated with pig manure (PM) as an unused biomass. Regarding the measurement of organic acids by high-performance liquid chromatography (HPLC), acetate and butyrate were increased in the C. cellulovorans medium containing 0.5% PM, while formate and lactate were decreased in it. Next, in comparison with carbon sources such as glucose, cellobiose, and acetate, cocultivation of C. cellulovorans and Methanosarcina mazei or microbial flora of me-thane production (MFMP) was performed in the C. cellulovorans medium. These results revealed that 0.5% acetate as the sole carbon source produced CH4 only by cocultivating C. cellulovorans and MFMP. Furthermore, MFMP was only cultivated with 1% acetate or 1% methane as a carbon source after precultivated with 0.5% glucose medium for 12 h. As a result, methane productivity of MFMP with 1% methanol medium was approximately eight times higher than that with 1% acetate medium. Finally, next-generation sequencing (NGS) analysis of MFMP after cultivation with 1% acetate or 1% methane was carried out. Interestingly, Methanofollis (0.211%) belonging to H2/CO2 -using methanogens (CO2 reduction pathway) was dominant in the 1% acetate medium for 72 h cultivation, whereas Methanosarcina siciliae (1.178%), M. barkeri (0.571%), and Methano-follis (0.490%) were major species in 1% methanol medium for 72 h cultivation. Since Methano-sarcina spp. are belonging to acetoclasts (acetoclastic pathway), methanol could promote to grow Methanosarcina spp. rather than acetate. Therefore, it seemed Methanosarcina spp. may play a key methanogenesis in MFMP. Thus, these results will provide important information for low cost biomethane production.

Drained peatlands are significant sources of the greenhouse gas (GHG) carbon dioxide. Rewetting is a proven strategy to protect carbon stocks; however, it can lead to increased emissions of the potent GHG methane. The response to rewetting of soil microbiomes as drivers of these processes is poorly understood, as are biotic and abiotic factors that control community composition. We analyzed the pro- and eukaryotic microbiomes of three contrasting pairs of minerotrophic fens subject to decade-long drainage and subsequent rewetting. Also, abiotic soil properties including moisture, dissolved organic matter, methane fluxes and ecosystem respiration rates. The composition of the microbiomes was fen-type-specific, but all rewetted sites showed higher abundance of anaerobic taxa compared to drained sites. Based on multi-variate statistics and network analyses we identified soil moisture as major driver of community composition. Furthermore, salinity drove the separation between coastal and freshwater fen communities. Methanogens were more than tenfold more abundant in rewetted than in drained sites, while their abundance was lowest in the coastal fen, likely due to competition with sulfate reducers. The microbiome compositions were reflected in methane fluxes from the sites. Our results shed light on the factors that structure fen microbiomes via environmental filtering.

As the global demand for water increases, so does the quantity of wastewater requiring treatment. Due to a relatively low carbon footprint, compared with conventional wastewater treatment technologies, anaerobic digestion (AD) was identified in the 1970s as a forerunner in the push for sustainability, when interest in sustainable technologies and renewable energy sources was first sparked. AD technology development ultimately resulted in the discovery of the ‘anaerobic granule’. It is a spontaneously-forming bio-aggregate of microbial cells capable of digesting pollutants and producing methane-rich biogas as a renewable source of bioenergy. The high settling velocity of such granules meant that AD systems could be operated as high-rate treatment processes, because the active, relatively-slow-growing, pollutant-removing biomass would be retained inside, and not washed out of, even bioreactors operated at extremely high volumetric loading rates. In the intervening years the emergence of the anaerobic ammonium oxidising (anammox) granule, aerobic granule, hydrogenic granule, oxygenic photogranule, and many other functionally-specialised granules, has opened new opportunities in wastewater treatment biotechnology. Whilst environmental engineering based around wastewater treatment is still a growing field of research and implementation, the granule (in all forms) is starting to catch the attention of microbial ecologists. It is a self-immobilised biofilm, with many of the properties of ‘conventional’ biofilms formed in Nature. However, as a single entity, a granule represents an entire community of microorganisms, competing or functioning cooperatively or in syntrophy. Together, inside a bioreactor, granules perform side-by-side arguably representing a meta-organism. Granules are gaining traction as the perfect samples for high-throughput studies on fundamental ecological concepts. Granular biofilms can be used to test hypotheses around drivers of diversity, community assembly, biofilm formation and maturation, community expansion and succession, community stress response, among others. This review outlines the history of three of the most influential types of granules: the anaerobic (methanogenic), aerobic and anammox granule. The main biochemical processes found in each type; their primary characteristics; and the typical makeup of the microbial community underpinning the processes are compared. Finally, the adoption of granules as the perfect ‘playground’ for experiments in microbial ecology is reviewed.

Coalbed Methane(CBM) production enhancement for single wells is a big problem to CBM industrialization. Low production is due to insufficient gas generation by thermogenic. Luckily, Biogenic gas was found in many areas and its supply is assumed to improve coalbed methane production. Therefore, microbial simulation experiment will demonstrate the effectiveness of the assumption. From microbial simulation experiment on different coal ranks, it is found that microbes can use coals to produce biogas under laboratory conditions. With different temperatures for different experiments, it turns out that the gas production at 35 ℃ is greater than that at 15℃,indicating that 35℃ is more suitable for microbes to produce gas. According to quantitative experiments, adding exogenous nutrients or exogenous bacteria can improve CBM production. Moreover, the production enhancement ratio can reach up to 115% under the condition of adding exogenous bacterial species, while the ratio for adding nutrients can be up to 144%.

Despite the extensive research conducted on ruminal methanogens and anti-methanogenic intervention strategies over the last 50 years, most of the currently researched enteric CH4 abatement approaches have shown limited efficacy. This is largely because of the complex nature of animal production and the ruminal environment, host genetic variability of CH4 production, and an incomplete understanding of the role of the ruminal microbiome in enteric CH4 emissions. Recent sequencing-based studies suggest the presence of methanogenic archaea in extra-gastrointestinal tract tissues, including respiratory and reproductive tracts of cattle. While these sequencing data require further verification by culture-dependent methods, the consistent identification of methanogens with relatively greater frequency in the airway and urogenital tract of cattle plus increasing appreciation of the microbiome-gut-organ axis highlight the potential interactions between ruminal and extra-gastrointestinal methanogenic communities. Thus, a traditional singular focus on ruminal methanogens may not be sufficient, and a holistic approach which takes into consideration of the transfer of methanogens between ruminal, extra-gastrointestinal, and environmental microbial communities is of necessity to develop more efficient and long-term ruminal CH4 mitigation strategies. In the present review, we provide a holistic survey of the methanogenic archaea present in different anatomical sites of cattle and discuss potential seeding sources of the ruminal methanogens.