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Polyhydroxyalkanoate-driven current generation via acetate by an anaerobic methanotrophic consortium
Xueqin Zhang1, Simon J McIlroy2, Igor Vassilev3
1Australian Centre for Water and Environmental Biotechnology (ACWEB, formerly AWMC), The University of Queensland, Brisbane 4072, Australia.
Water Research
|June 20, 2022
Summary
Anaerobic oxidation of methane (AOM) is key for mitigating methane emissions. This study reveals that
Area of Science:
- Microbial Ecology
- Biogeochemistry
- Environmental Science
Background:
- Anaerobic oxidation of methane (AOM) is a critical microbial process reducing methane emissions.
- Anaerobic methanotrophic archaea (ANME) mediate AOM via extracellular electron transfer (EET), but mechanisms are unclear.
- Understanding EET is vital for microbial methane mitigation strategies.
Purpose of the Study:
- Investigate electron and carbon flow in an anaerobic methanotrophic consortium.
- Elucidate the role of acetate and intracellular storage compounds in AOM.
- Determine the metabolic capabilities of 'Candidatus Methanoperedens nitroreducens'.
Main Methods:
- Utilized a methane-fed microbial electrolysis cell (MEC).
- Performed electrochemical characterization and stoichiometric calculations.
- Employed stable isotope-based assays to track carbon and electron flow.
Main Results:
- Identified acetate as a likely intermediate, supporting Geobacter growth.
- Demonstrated acetate is not directly produced from methane.
- Showed 'Ca. M. nitroreducens' utilizes stored polyhydroxybutyrate (PHB) and extracellular polymeric substances (EPSs) for energy and carbon, even without methane.
- Confirmed 'Ca. M. nitroreducens' can donate acetate as an electron carrier.
Conclusions:
- 'Candidatus Methanoperedens nitroreducens' exhibits significant metabolic flexibility.
- Stored PHB and EPS breakdown contribute to current generation in AOM.
- Acetate donation by ANME expands understanding of EET mechanisms in natural environments.
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