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Detecting active methanogenic populations on rice roots using stable isotope probing
Yahai Lu1, Tillmann Lueders, Michael W Friedrich
1Max-Planck-Institut für terrestrial Mikrobiologie, Karl-von-Frisch-Str., 35043 Marburg, Germany.
Environmental Microbiology
|February 3, 2005
Summary
Active methane-producing microbes in rice roots shift based on hydrogen levels and buffer type. Methanogenic populations, including Rice Cluster-I and Methanosarcinaceae, were identified and their activity tracked using stable isotope probing.
Area of Science:
- Microbial Ecology
- Environmental Microbiology
- Biogeochemistry
Background:
- Methane (CH4) production in rice paddies is a significant source of greenhouse gas emissions.
- Carbon dioxide (CO2) reduction is a primary pathway for methanogenesis in rice root environments.
- Identifying the specific microorganisms responsible for CH4 formation is crucial for understanding and mitigating these emissions.
Purpose of the Study:
- To identify the active methanogenic archaeal populations in soil-free rice root systems.
- To investigate how different conditions, such as hydrogen (H2) concentration and buffer type, influence these microbial communities and their activity.
- To determine the relative contributions of different methanogenic groups to CH4 production under varying experimental setups.
Main Methods:
- Incubation of soil-free rice roots under controlled atmospheres (H2/13CO2 or N2/13CO2) with different buffers (phosphate or carbonate).
- Extraction and fractionation of nucleic acids using caesium trifluoroacetate equilibrium density gradient centrifugation.
- Community analysis via terminal restriction fragment length polymorphism (T-RFLP) and 16S rRNA gene sequencing of fractionated DNA.
- Tracking of microbial activity using stable isotope probing ([13C]DNA) and rRNA analysis over time.
Main Results:
- Methanosarcinaceae and Rice Cluster-I (RC-I) were dominant with carbonate buffer and N2 headspace.
- [13C]DNA analysis indicated higher activity of RC-I compared to Methanosarcinaceae under these conditions.
- High H2 concentrations (80%) initially suppressed RC-I activity and CH4 production, but Methanosarcinaceae later became prevalent, increasing CH4 production.
- Phosphate buffer inhibited Methanosarcinaceae, leading to Methanobacteriaceae dominance and lower CH4 production compared to carbonate buffer.
Conclusions:
- The active methanogenic communities in rice roots are dynamic and responsive to environmental factors like H2 availability and buffer composition.
- Rice Cluster-I and Methanosarcinaceae play key roles in rice root methanogenesis, with their activity modulated by experimental conditions.
- Understanding these shifts is vital for predicting and managing methane emissions from rice cultivation.