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January 09, 2017


Electron microscopy image of two distinct microbes that can, when in close association, produce electric current. Researchers studied metabolic processes in microbes for potential applications to waste treatment and bioenergy production. [Image courtesy Ha et al. 2017. DOI: 10.1038/ncomms13924. (CC-BY 4.0)]


Microbial Communities Thrive by Transferring Electrons

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

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 called syntrophic anaerobic photosynthesis, 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 for use in waste treatment and bioenergy production.

Summary
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 of 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 the Environmental Molecular Sciences Laboratory (EMSL), a Department of Energy Office of Science user facility. 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.

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
beyenal@wsu.edu

Alice Dohnalkova
EMSL
Alice.Dohnalkova@pnnl.gov

Funding
This work was supported by the U.S. Department of Energy (DOE), Office of Biological and Environmental Research, Genomic Science program and is a contribution of the PNNL Foundational Scientific Focus Area (FSFA). A portion of this work was conducted at EMSL, a DOE Office of Science user facility.

Publication
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 (2017). DOI:10.1038/ncomms13924. (Reference link)

Related Links
EMSL Article
WSU Article

Topic Areas:

  • Research Area: Carbon Cycle, Biosequestration
  • Research Area: DOE Environmental Molecular Sciences Laboratory (EMSL)
  • Research Area: Genomic Analysis and DNA Sequencing
  • Research Area: Microbes and Communities
  • Research Area: Biological Engineering
  • Mission Science: Sustainable Biofuels

Division: SC-23.1 Climate and Environmental Sciences Division, BER,SC-23.2 Biological Systems Science Division, BER


 

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