New Metabolic Pathway Discovered in Methane-Consuming Bacteria
Methane is an essential component of the global carbon cycle and one of the most powerful greenhouse gases. Major uncertainties remain as to how global climate change will impact the release of carbon stored in ecosystems, particularly in terms of the balance between CO2 and methane entering the atmosphere. Recent technological advances in natural gas extraction from the deep subsurface also have vastly increased the supply of methane for energy production and potentially as an alternate carbon source for synthesis of fuels and other value-added chemicals. These developments have focused increased attention on biological processes that involve methane. For example, aerobic methane-consuming bacteria (methanotrophs) perform key ecosystem processes that affect methane release and represent a potential biological platform for methane-based industrial biocatalysis. In a new study, U.S. Department of Energy investigators at the University of Washington used a multifaceted systems biology approach to examine methane utilization by the methanotrophic bacterium Methylomicrobium alcaliphilum. Their results reveal a previously unknown metabolic pathway in which methane uptake is tightly coupled with glycolytic carbon metabolism, resulting in a novel form of fermentation-based methanotrophy. Under oxygen-limited conditions, this pathway produces acetate and other organic compounds as endproducts rather than CO2, which had been thought to be the sole product of methanotrophic metabolism. This discovery significantly alters our understanding of the role of methanotrophs in environmental carbon cycle processes and presents new opportunities for metabolic engineering of these organisms as platforms for biological conversion of methane to advanced biofuels and other products.
Kalyuzhnaya, M. G., S. Yang, O. N. Rozova, N. E. Smalley, J. Clubb, A. Lamb, G. A. Nagana Gowda, D. Raftery, Y. Fu, F. Bringel, S. Vuilleumier, D. A. C. Beck, Y. A. Trotsenko, V. N. Khmelenina, and M. E. Lidstrom. 2013. “Highly Efficient Methane Biocatalysis Revealed in a Methanotrophic Bacterium,” Nature Communications 4, 2785. DOI: 10.1038/ncomms3785.