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

“ Even if a very modest yield is used for estimating the average rate of electron discharge, the transfer of solar energy to the environment via cyanobacterial electrogenic pathway could proceed at the rate of ∼9 TW on a global scale. Therefore, the electrogenic pathway appears to be an important microbiological conduit of solar energy into the biosphere and could have significant impact on a global scale. ”

“ The differences in the ratio of photosynthetic pigments in individual genera could explain the different amplitude of the electrogenic response between Nostoc and Lyngbya under the blue light (Fig. 6) .
While it is tempting to speculate electrogenic activity may provide a means of shedding excess energy under intense light, other functions, such as a role in carbon fixation, might also be possible. For efficient carbon fixation, cyanobacteria actively import HCO3− using membrane-spanning transporters [27] . ”

“ The anode potential was found to oscillate as a function of illumination cycles providing direct evidence that cyanobacteria deposit electrons onto anode surface when exposed to light. Light-dependent deposition of electrons makes the anode potential less positive compared to the potential in the dark which results in the increase in MFC voltage during the light phase. The control anode devoid of photosynthetic biofilm showed no response to illumination (Fig. 3) . ”

“ 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 funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
References 1 2 3 Waterbury JB, Watson SW, Guillard RRL, Brand LE. Widespread occurrence of a unicellular, marine, planktonic, cyanobacterium. Nature. ”

“ Biochim Biophys Acta. 2003;1604:115–123.127657681 2 Zou Y, Pisciotta J, Baskakov IV. Nanostructured polypyrrole-coated anode for sun-powered microbial fuel cells. Bioelectrochem in press 2009↑ Bennetto HP, Stirling JL, Tanaka K, Vega CA. Anodic reactions in microbial fuel cells. Biotechno Bioeng. ”