5:15 PM - 7:15 PM
[BCG05-P05] Dynamics of Potential Active Methanogens and Methanotrophs in Constructed Wetlands: A DNA Stable Isotope Probing Approach
Keywords:Constructed wetland, DNA Stable-isotope probing, pmoA, mcrA;, Methane
Constructed wetlands (CWs) are increasingly being implemented as nature-based solutions for water treatment and carbon (C) sequestration. However, their role in the global methane (CH4) budget remains uncertain, as CH4 emissions from these systems could potentially offset their C sink function. The net CH4 balance in CWs is influenced by the interaction between methanogens and methanotrophs. Given the growing demand for CWs, it is crucial to determine whether these systems act as CH4 sinks or sources and to identify the key microbial players that drive CH4 flux dynamics.
To address this knowledge gap, this study employed DNA-stable isotope probing (DNA-SIP) to target the mrcA and pmoA function gene in order to identify potential active methanogens and methanotrophs across CWs of different ages in Taiwan. Compared to RNA-based approaches (i.e. metatranscriptomic analysis), DNA-SIP offers a more cost-effective and targeted method for identifying metabolically active microbial populations, as it selectively labels organisms that incorporate labeled substrates into their DNA. This approach overcomes challenges associated with high sequencing costs and the transient nature of RNA signals, providing a more direct assessment of functionally active microbial communities. The results indicate that methanotrophic processes could potentially offset up to 25% of CH4 emissions. The methanogenic potential in the 2-5 cm soil layer is 0-0.41 micromole CH4 g-1 soil hr-1, while the methane oxidation potential in the 0-2 cm soil layer is 0.05-0.11 micromole CH4 g-1 soil hr-1. These findings highlight the importance of these processes in regulating CH4 fluxes within the CW.
DNA-SIP further identified the genera Methylomonas, Methylobacter, and Methylosarcina as dominant potential active Type Ia methanotrophs, recognized for their high capacity for CH4 oxidation. Meanwhile, the genera Methanosarcina, Methanosaeta, and Methanolinea were prevalent among potential active methanogens, suggesting that both acetoclastic and hydrogenotrophic pathways contribute to CH4 production in these systems. Notably, the concentrations of ammonium and sulfate influenced niche differentiation among methanotrophs, suggesting potential strategies for CH4 mitigation through the management of inflow water.
These findings highlight the dynamic nature of CH4 cycling in CWs and emphasize the importance of balancing methanotrophic and methanogenic activities to regulate CH4 fluxes. As the adoption of CWs expands, optimizing their design to enhance CH4 oxidation while minimizing methanogenesis will be crucial for maximizing their role as carbon sinks rather than CH4 sources.
To address this knowledge gap, this study employed DNA-stable isotope probing (DNA-SIP) to target the mrcA and pmoA function gene in order to identify potential active methanogens and methanotrophs across CWs of different ages in Taiwan. Compared to RNA-based approaches (i.e. metatranscriptomic analysis), DNA-SIP offers a more cost-effective and targeted method for identifying metabolically active microbial populations, as it selectively labels organisms that incorporate labeled substrates into their DNA. This approach overcomes challenges associated with high sequencing costs and the transient nature of RNA signals, providing a more direct assessment of functionally active microbial communities. The results indicate that methanotrophic processes could potentially offset up to 25% of CH4 emissions. The methanogenic potential in the 2-5 cm soil layer is 0-0.41 micromole CH4 g-1 soil hr-1, while the methane oxidation potential in the 0-2 cm soil layer is 0.05-0.11 micromole CH4 g-1 soil hr-1. These findings highlight the importance of these processes in regulating CH4 fluxes within the CW.
DNA-SIP further identified the genera Methylomonas, Methylobacter, and Methylosarcina as dominant potential active Type Ia methanotrophs, recognized for their high capacity for CH4 oxidation. Meanwhile, the genera Methanosarcina, Methanosaeta, and Methanolinea were prevalent among potential active methanogens, suggesting that both acetoclastic and hydrogenotrophic pathways contribute to CH4 production in these systems. Notably, the concentrations of ammonium and sulfate influenced niche differentiation among methanotrophs, suggesting potential strategies for CH4 mitigation through the management of inflow water.
These findings highlight the dynamic nature of CH4 cycling in CWs and emphasize the importance of balancing methanotrophic and methanogenic activities to regulate CH4 fluxes. As the adoption of CWs expands, optimizing their design to enhance CH4 oxidation while minimizing methanogenesis will be crucial for maximizing their role as carbon sinks rather than CH4 sources.