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article imageBacteria used to produce electricity

By Tim Sandle     Oct 15, 2013 in Science
Scientists have examined two important bacterial forms, demonstrating their ability to produce electricity by coordinating their metabolic activities.
The remarkable find is that the light-sensitive green sulfur bacterium Chlorobium can act in tandem with Geobacter, an anode respiring bacterium. The result is a light-responsive form of electricity generation and the production of a current.
The electrons Geobacter acquires from its photosynthetic partner Chlorobium can be measured and collected in the form of electricity, using a device known as a microbial fuel cell (MFC), which is a kind of biological battery. An MFC is a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature.
A typical microbial fuel cell consists of anode and cathode compartments separated by a cation (positively charged ion) specific membrane. In the anode compartment, fuel is oxidized by microorganisms, generating carbon dioxide, electrons and protons. Electrons are transferred to the cathode compartment through an external electric circuit, while protons are transferred to the cathode compartment through the membrane. Electrons and protons are consumed in the cathode compartment, combining with oxygen to form water.
The newly researched process works by mixing conditions of light and dark. Chlorobium bacteria gather energy from light in order to fix carbon dioxide and fuel their metabolism. During dark phases however, they sustain themselves by switching from photosynthesis to dark fermentation, using energy they have stored. During periods of darkness, anode respiring Geobacter gains electrons, thereby producing the observed rise in electrical current.
Scientists hope that microbial fuel cells may one day generate clean electricity from various streams of organic waste, simply by exploiting the electron-transfer abilities of various microorganisms. The researchers conclude that further investigation of these environmentally relevant and physiologically unique organisms is warranted.
The study was carried out at Arizona State University's Biodesign Institute, Jonathan Badalamenti. The findings have been published in the journal Biotechnology and Bioengineering. The paper is titled “Coupling dark metabolism to electricity generation using photosynthetic cocultures.”
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