From EMSL: “Microbial Communities Thrive by Transferring Electrons”



February 03, 2017 [Blew right by tis when it first came out. Glad to see they re-issued it.]
Haluk Beyenal
Washington State University

Alice Dohnalkova

New cooperative photosynthesis studied for applications to waste treatment and bioenergy production. No image credit.

The Science

Photosynthetic bacteria are major primary producers on Earth, using sunlight to convert inorganic compounds in the environment into more complex organic compounds that fuel all living systems on the planet. A team of researchers recently discovered a new microbial metabolic process, which they termed syntrophic anaerobic photosynthesis, and which could represent an important, widespread form of carbon metabolism in oxygen-depleted zones of poorly mixed freshwater lakes.

The Impact

The discovery of syntrophic anaerobic photosynthesis reveals new possibilities for bioengineering microbial communities that could be used for waste treatment and bioenergy production.


Almost all life on Earth relies directly or indirectly on primary production—the conversion of inorganic compounds in the environment into organic compounds that store chemical energy and fuel the activity of organisms. Nearly half the global primary productivity occurs through photosynthetic carbon dioxide (CO2) fixation by sulfur bacteria and cyanobacteria. In oxygen-depleted environments, photosynthetic bacteria use inorganic compounds such as water, hydrogen gas and hydrogen sulfide to provide electrons needed to convert CO2 into organic compounds. These organic compounds also make their way into the food web, where they support the growth of heterotrophs—organisms that cannot manufacture their own food. A recent study revealed a new 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 (PNNL), 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 at EMSL, the Environmental Molecular Sciences Laboratory, a DOE Office of Science user facility.

Quanta scanning electron microscope

FEI Tecnai T-12 cryo-transmission electron microscope

Their analysis revealed that a heterotrophic bacterial species, Geobacter sulfurreducens, directly transfers electrons to a photosynthetic bacterial species, Prosthecochloris aestuarii, which uses electrons to fix CO2 into cell material. At the same time, donating electrons allows G. sulfurreducens to support its own metabolic needs by converting acetate into CO2 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.

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.” 2017 Nature Communications doi:10.1038/ncomms13924

See the full article here .

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