Methanogen

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

Evidence of Novel Phylogenetic Lineages of Methanogenic Archaea from Hypersaline Microbial Mats

Abstract: Methanogenesis in hypersaline and high-sulfate environments is typically dominated by methylotrophic methanogens because sulfate reduction is thermodynamically favored over hydrogenotrophic methanogenesis in these environments. We characterized the community composition of methanogenic archaea in both unmanipulated and incubated microbial mats from different hypersaline environments in Baja California Sur, Mexico. Clone libraries of methyl coenzyme-M reductase (mcrA) sequences and DGGE band patterns of 16S rRNA and mcrA sequences showed that the methanogen community in these microbial mats is dominated by methylotrophic methanogens of the genus Methanohalophilus. However, phylogenetic analyses of mcrA sequences from these mats also revealed two new lineages corresponding to putative hydrogenotrophic methanogens related with the strictly hydrogenotrophic order Methanomicrobiales. Stimulated methane production under decreased salinity and sulfate concentrations also suggested the presence of hydrogenotrophic methanogens in these samples. The relative abundance of mcrA gene and transcripts, estimated by SYBR green I qPCR assays, suggested the activity of different phylogenetic groups of methanogens, including the two novel clusters, in unmanipulated samples of hypersaline microbial mats. Using geochemical and molecular approaches, we show that substrate limitation and values of salinity and sulfate higher than 3 % and 25 mM (respectively) are potential environmental constraints for methanogenesis in these environments. Microcosm experiments with modifications of salinity and sulfate concentrations and TMA addition showed that upper salt and sulfate concentrations for occurrence of methylotrophic methanogenesis were 28 % and 263 mM, respectively. This study provides phylogenetic information about uncultivated and undescribed methanogenic archaea from hypersaline environments.

Co-occurrence network analysis reveals thermodynamics-driven microbial interactions in methanogenic bioreactors

Abstract: Methanogenic bioreactors have been applied to treat purified terephthalic acid (PTA) wastewater containing complex aromatic compounds, such as terephthalic acid, para-toluic acid and benzoic acid. This study characterized the interaction of microbial populations in 42 samples obtained from 10 PTA-degrading methanogenic bioreactors. Approximately, 54 dominant populations (11 methanogens, 8 syntrophs and 35 functionally unknown clades) that represented 73.9% of total 16S rRNA gene iTag sequence reads were identified. Co-occurrence analysis based on the abundance of dominant OTUs showed two non-overlapping networks centred around aromatic compound- (group AR: Syntrophorhabdaceae, Syntrophus and Pelotomaculum) and fatty acid- (group FA: Smithella and Syntrophobacter) degrading syntrophs. Group AR syntrophs have no direct correlation with hydrogenotrophic methanogens, while those from group FA do. As degradation of aromatic compounds has a wider thermodynamic window than fatty acids, Group AR syntrophs may be less influenced by fluctuations in hydrogenotrophic methanogen abundance or may non-specifically interact with diverse methanogens. In both groups, network analysis reveals full-scale- and lab-scale-specific uncultivated taxa that may mediate interactions between syntrophs and methanogens, suggesting that those uncultivated taxa may support the degradation of aromatic compounds through uncharted ecophysiological traits. These observations suggest that organisms from multiple niches orchestrate their metabolic capacity in multiple interaction networks to effectively degrade PTA wastewater.

A novel fingerprint method to assess the diversity of methanogens in microbial systems

Abstract: Understanding the ecology of methanogens in natural and engineered environments is a prerequisite to predicting or managing methane emissions. In this study, a novel high-throughput fingerprint method was developed for determining methanogen diversity and relative abundance within environmental samples. The method described here, designated amplicon length heterogeneity PCR of the mcrA gene (LH-mcrA), is based on the natural length variation in the mcrA gene. The mcrA gene encodes the alpha-subunit of the methyl-coenzyme M reductase, which is involved in the terminal step of methane production by methanogens. The methanogenic communities from stored swine and dairy manures were distinct from each other. To validate the method, methanogenic communities in a plug flow-type bioreactor (PFBR) treating swine manure were characterized using LH-mcrA method and correlated to mcrA gene clone libraries. The diversity and relative abundance of the methanogenic groups were assessed. Methanobrevibacter, Methanosarcinaceae, Methanoculleus, Methanogenium, Methanocorpusculum and one unidentified group were assigned to particular LH-mcrA amplicons. Particular phylotypes related to Methanoculleus were predominant in the last compartment of the PFBR where the bulk of methane was produced. LH-mcrA method was found to be a reliable, fast and cost-effective alternative for diversity assessment of methanogenic communities in microbial systems.

Isolation and characterization of a motile hydrogenotrophic methanogen from rice paddy field soil in Japan.

Abstract: A hydrogenotrophic motile methanogen was isolated from flooded Japanese paddy field soil. Anaerobic incubation of the paddy soil on H2–CO2 at 20°C led to the enrichment of symmetrically curved motile autofluorescent rods. The methanogenic strain TM20-1 isolated from the culture was halotolerant and utilized H2–CO2, 2-propanol-CO2, or formate as a sole methanogenic substrate. Based on the 16S rRNA gene sequence similarity (94.8%) with Methanospirillum hungateii, and on the physiological and phenotypic characteristics, TM20-1 was suggested to be a newly identified species belonging to the genus Methanospirillum. This is the first report of isolation of the genus Methanospirillum strain from a rice paddy field.