Journal Article

Light-Dependent Electrogenic Activity of Cyanobacteria

Baskakov, Ilia V., Zou, Yongjin, Pisciotta, John M.

2010

Overview

Cyanobacteria account for 20-30% of Earth's primary photosynthetic productivity and convert solar energy into biomass-stored chemical energy at the rate of approximately 450 TW [1]. These single-cell microorganisms are resilient predecessors of all higher oxygenic phototrophs and can be found in self-sustaining, nitrogen-fixing communities the world over, from Antarctic glaciers to the Sahara desert [2]. Here we show that diverse genera of cyanobacteria including biofilm-forming and pelagic strains have a conserved light-dependent electrogenic activity, i.e. the ability to transfer electrons to their surroundings in response to illumination. Naturally-growing biofilm-forming photosynthetic consortia also displayed light-dependent electrogenic activity, demonstrating that this phenomenon is not limited to individual cultures. Treatment with site-specific inhibitors revealed the electrons originate at the photosynthetic electron transfer chain (P-ETC). Moreover, electrogenic activity was observed upon illumination only with blue or red but not green light confirming that P-ETC is the source of electrons. The yield of electrons harvested by extracellular electron acceptor to photons available for photosynthesis ranged from 0.05% to 0.3%, although the efficiency of electron harvesting likely varies depending on terminal electron acceptor. The current study illustrates that cyanobacterial electrogenic activity is an important microbiological conduit of solar energy into the biosphere. The mechanism responsible for electrogenic activity in cyanobacteria appears to be fundamentally different from the one exploited in previously discovered electrogenic bacteria, such as Geobacter, where electrons are derived from oxidation of organic compounds and transported via a respiratory electron transfer chain (R-ETC) [3], [4]. The electrogenic pathway of cyanobacteria might be exploited to develop light-sensitive devices or future technologies that convert solar energy into limited amounts of electricity in a self-sustainable, CO(2)-free manner.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Anabaena variabilis / Antarctic glaciers / Biofilms / Biofilms - radiation effects / Biomass energy production / Biomedical engineering / Biosphere / Biotechnology/Applied Microbiology / Carbon dioxide / Chains / Chemical energy / Consortia / Cyanobacteria / Cyanobacteria - physiology / Cyanobacteria - radiation effects / Cytochrome / Desert environments / Deserts / Earth / Ecology / Ecology/Conservation and Restoration Ecology / Ecology/Environmental Microbiology / Ecology/Marine and Freshwater Ecology / Electricity / Electrodes / Electron transfer / Electron transport / Electrons / Electrophoresis, Agar Gel / Energy / Energy (Physics) / Forming / Geobacter / Glaciers / Hypotheses / Illumination / Light / Light effects / Lyngbya / Marine and Aquatic Sciences/Ecology / Marine and Aquatic Sciences/Microbiology / Microbiology / Microbiology/Environmental Microbiology / Microorganisms / Nitrogen / Nitrogen fixation / Organic compounds / Oxidation / Photons / Photoreceptors / Photosynthesis / Photosynthesis - radiation effects / Phototrophic microorganisms / Plant biochemistry / Solar energy / Solar energy conversion / Synechocystis / Time Factors / Water