July 2014

New Metabolic Pathway Discovered in Methane-Consuming Bacteria

Opportunities emerge for using microbes to convert the gas to biofuels and other products.

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Image reprinted by permission from Macmillan Publishers Ltd. from Kalyuzhnaya, M. G., et al. “Highly efficient methane biocatalysis revealed in a methanotrophic bacterium,” Nat. Commun. 4, 2785. Copyright 2013.External link

Research suggests that methane (CH4) utilization by the bacterium Methylomicrobium alcaliphilum under low oxygen (O2­) conditions may involve switching to a new fermentation-based mode that leads to the formation of formate, acetate, succinate, lactate, hydrogen, and hydroxybutyrate as end products.

The Science

Methane (CH4) is an essential component of the global carbon cycle and one of the most powerful greenhouse gases. To better understand microbial CH4 utilization, researchers used a multifaceted systems biology approach to examine Methylomicrobium alcaliphilum, a methanotroph (i.e., an aerobic bacterium that consumes CH4)­. The study’s results reveal a previously unknown metabolic pathway in which CH4 uptake is tightly coupled with glycolytic carbon metabolism, resulting in a new form of fermentation-based methanotrophy.

The Impact

This discovery by Department of Energy investigators at the University of Washington significantly alters the understanding of methanotrophs’ role in environmental carbon cycling processes. Results also present new opportunities for metabolic engineering of these organisms as platforms for biological conversion of CH4 to advanced biofuels and other products.

Summary

Major uncertainties remain as to how global climate change will affect the release of carbon stored in ecosystems, particularly in terms of the balance between carbon dioxide (CO2) and CH4 entering the atmosphere. Recent technological advances in natural gas extraction from the deep subsurface also have vastly increased the supply of CH4 for energy production and as a possible alternative carbon source for the synthesis of fuels and other value-added chemicals. These developments have focused increased attention on biological processes that involve CH4. For example, methanotrophs perform key ecosystem processes that affect CH4 release and represent a potential biological platform for CH4-based industrial biocatalysis. Under oxygen-limited conditions, the newly discovered metabolic pathway produces acetate and other organic compounds as end products rather than CO2, which had been thought to be the sole product of methanotrophic metabolism.

Contact

M.G. Kalyuzhnaya
Shandong Province Key Laboratory of Applied Mycology, School of Life Sciences, Qingdao Agricultural University, China and Key Laboratory of Systems Bioengineering, Ministry of Education, Tianjin University, China.
marina.kalyuzh@gmail.com

Funding

The work was supported by the National Science Foundation (MCB-0842686), the Department of Energy (DE-SC0005154), CRDF Global (RUB1-2946-PU-09), and the Russian Foundation for Basic Research (RFBR 12-04-32122-a). Support from LABGeM and France Genomique for use of the online comparative genomics analysis platform MicroScope is gratefully acknowledged.

Publications

Kalyuzhnaya, M. G., et al. “Highly efficient methane biocatalysis revealed in a methanotrophic bacterium,” Nat. Commun. 4, 2785 (2013). [DOI: 10.1038/ncomms3785].

Highlight Categories

Program: BER, BSSD

Performer/Facility: University

Additional: Collaborations, Non-DOE Interagency Collaboration, International Collaboration

Last modified: 8/1/2014 1:19:56 PM