Methanogen

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

A microbial functional group-based module for simulating methane production and consumption: Application to an incubated permafrost soil

Abstract: Accurately estimating methane (CH4) flux in terrestrial ecosystems is critically important for investigating and predicting biogeochemistry-climate feedbacks. Improved simulations of CH4 flux require explicit representations of the microbial processes that account for CH4 dynamics. A microbial functional group-based module was developed, building on the decomposition subroutine of the Community Land Model 4.5. This module considers four key mechanisms for CH4 production and consumption: methanogenesis from acetate or from single-carbon compounds and CH4 oxidation using molecular oxygen or other inorganic electron acceptors. Four microbial functional groups perform these processes: acetoclastic methanogens, hydrogenotrophic methanogens, aerobic methanotrophs, and anaerobic methanotrophs. This module was used to simulate dynamics of carbon dioxide (CO2) and CH4 concentrations from an incubation experiment with permafrost soils. The results show that the model captures the dynamics of CO2 and CH4 concentrations in microcosms with top soils, mineral layer soils, and permafrost soils under natural and saturated moisture conditions and three temperature conditions of −2°C, 3°C, and 5°C (R2 > 0.67; P < 0.001). The biases for modeled results are less than 30% across the soil samples and moisture and temperature conditions. Sensitivity analysis confirmed the importance of acetic acid's direct contribution as substrate and indirect effects through pH feedback on CO2 and CH4 production and consumption. This study suggests that representing the microbial mechanisms is critical for modeling CH4 production and consumption; it is urgent to incorporate microbial mechanisms into Earth system models for better predicting trace gas dynamics and the behavior of the climate system.

Methylphosphonate metabolism by Pseudomonas sp. populations contributes to the methane oversaturation paradox in an oxic freshwater lake.

Abstract: The 'CH4 oversaturation paradox' has been observed in oxygen-rich marine and lake waters, and viewed to significantly contribute to biosphere cycling of methane, a potent greenhouse gas. Our study focused on the intriguing well-defined pelagic methane enriched zone (PMEZ) in freshwater lakes. Spiking Yellowstone Lake PMEZ samples with 13 C-labeled potential methanogenesis substrates found only 13 C-methylphosphonate (MPn) resulted in 13 CH4 generation. In 16S rRNA gene Illumina libraries, four Pseudomonas sp. operational taxonomic units surprisingly accounted for ∼11% abundance in the PMEZ community. Pseudomonas sp. isolates were also obtained from MPn enrichments with PMEZ water; they were most aggressive in MPn metabolism and their 16S rRNA gene sequences matched 35% of the Illumina PMEZ Pseudomonas reads. Further, two key genes encoding C-P lyase (phnJL, an important enzyme for dealkylation of MPn), were only amplifiable from PMEZ DNA and all PCR generated phnJL clones matched those of the Pseudomonas sp. isolates. Notably, methanogen 16S rRNA signatures were absent in all Illumina libraries and mcrA was not detected via PCR. Collectively, these observations are consistent with the conclusion that MPn metabolism contributes significantly to CH4 oversaturation in Yellowstone Lake and likely other oxic freshwater lake environments, and that Pseudomonas sp. populations are critical participants.

Persistence of Methanosaeta populations in anaerobic digestion during process instability

Abstract: Anaerobic digestion is a sustainable technology for the treatment of organic waste and production of biogas. Acetoclastic methanogenesis accounts for the majority of methane production in anaerobic digestion. Therefore, sustaining robust acetoclastic methanogens is important for stable process performance. Due to faster growth kinetics at high acetate concentrations, it has been considered that Methanosarcina would be more prevalent than Methanosaeta in unstable anaerobic digestion processes which frequently experience high acetate levels. Methanogen population dynamics were monitored in multiple continuous anaerobic digesters for 500 days. Results from quantitative polymerase chain reaction analysis show that Methanosaeta dominated over Methanosarcina in anaerobic digestion at high acetate levels up to 44 mM, suggesting the potential of Methanosaeta as a robust and efficient acetoclastic candidate for resilient anaerobic methane conversion. Further efforts are needed to identify mechanisms contributing to the unexpected competitiveness of these methanogens at high acetate levels observed in this study.