Turning Waste into Fuels, Microbial Style

A newly discovered metabolic process linking different bacteria in a community could enhance bioenergy production.

Two distinct microbes can, when in close association, produce an electric current, according to researchers who studied metabolic processes. This work has potential applications to waste treatment and bioenergy production.

The Science

Life on this planet is fueled by sugars and compounds made via photosynthesis. Photosynthetic bacteria use light and turn carbon dioxide to produce such complex sugars. A team of researchers discovered a new way in which microbes produce these compounds. The new microbial metabolic process is called syntrophic anaerobic photosynthesis. It could be a vital, widespread form of capturing and processing carbon in oxygen-depleted environments.

The Impact

Syntrophic anaerobic photosynthesis reveals options for tailoring microbial communities. The groupings could help treat waste and produce energy. The challenges of treating wastewater is obvious in the average utility bill. Today’s treatment methods often use energy to remove carbon-based pollutants. Bacterial communities could turn carbon into fuels and electricity. This work could, one day, offer cost and energy savings to sanitation firms.


Almost all life on Earth relies directly or indirectly on the conversion of inorganic compounds in the environment into organic compounds that store chemical energy and fuel the activity of organisms. Nearly half of such conversion occurs through photosynthetic carbon dioxide fixation by sulfur bacteria and cyanobacteria. In oxygen-depleted environments, photosynthetic bacteria use water, hydrogen sulfide, or other compounds to provide electrons needed to convert carbon dioxide into organic compounds. These organic compounds feed heterotroph bacteria—organisms that cannot manufacture their own food. New research has revealed a metabolic process, called syntrophic anaerobic photosynthesis, in which photosynthetic and heterotrophic bacteria cooperate to support one another’s growth in oxygen-depleted environments. Researchers from Washington State University, Pacific Northwest National Laboratory, China University of Geoscience, and Southern Illinois University made this discovery using the Quanta scanning electron microscope and the FEI Tecnai T-12 cryo-transmission electron microscope. These microscopes are at the Environmental Molecular Sciences Laboratory, a Department of Energy Office of Science user facility. The team’s analysis revealed that a heterotrophic bacterial species, Geobacter sulfurreducens, directly transfers electrons to a photosynthetic bacterial species, Prosthecochloris aestuarii, which uses electrons to fix carbon dioxide into cell material. At the same time, donating electrons allows G. sulfurreducens to support its own metabolic needs by converting acetate into carbon dioxide and water. This potentially widespread, symbiotic form of metabolism, which links anaerobic photosynthesis directly to anaerobic respiration, could be harnessed to develop new strategies for waste treatment and bioenergy production.


BER PM Contacts
Roland Hirsch (FSFA), SC-23.2, 301-903-9009
Paul Bayer (EMSL), SC-23.1, 301-903-5324

PI Contacts
Haluk Beyenal
Washington State University

Alice Dohnalkova


This work was supported by the U.S. Department of Energy (DOE), Office of Science, Office of Biological and Environmental Research, Genomic Science program and is a contribution of the Pacific Northwest National Laboratory Foundational Scientific Focus Area. A portion of this work was conducted at the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility.


P.T. Ha, S.R. Lindemann, L. Shi, A.C. Dohnalkova, J.K. Fredrickson, M.T. Madigan, and H. Beyenal, “Syntrophic anaerobic photosynthesis via direct interspecies electron transfer.” Nature Communications 8, article 13924 (2017). [DOI: 10.1038/ncomms13924]

Related Links

Environmental Molecular Sciences Laboratory research highlight: Microbial communities thrive by transferring electrons

Washington State University news release: Researchers discover unique microbial photosynthesis

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