Applied Microbiology and Biotechnology

, Volume 91, Issue 2, pp 377–385 | Cite as

Role of the photosynthetic electron transfer chain in electrogenic activity of cyanobacteria

  • John M. Pisciotta
  • YongJin Zou
  • Ilia V. BaskakovEmail author
Applied Microbial and Cell Physiology


Certain anaerobic bacteria, termed electrogens, produce an electric current when electrons from oxidized organic molecules are deposited to extracellular metal oxide acceptors. In these heterotrophic “metal breathers”, the respiratory electron transport chain (R-ETC) works in concert with membrane-bound cytochrome oxidases to transfer electrons to the extracellular acceptors. The diversity of bacteria able to generate an electric current appears more widespread than previously thought, and aerobic phototrophs, including cyanobacteria, possess electrogenic activity. However, unlike heterotrophs, cyanobacteria electrogenic activity is light dependent, which suggests that a novel pathway could exist. To elucidate the electrogenic mechanism of cyanobacteria, the current studies used site-specific inhibitors to target components of the photosynthetic electron transport chain (P-ETC) and cytochrome oxidases. Here, we show that (1) P-ETC and, particularly, water photolysed by photosystem II (PSII) is the source of electrons discharged to the environment by illuminated cyanobacteria, and (2) water-derived electrons are transmitted from PSII to extracellular electron acceptors via plastoquinone and cytochrome bd quinol oxidase. Two cyanobacterial genera (Lyngbya and Nostoc) displayed very similar electrogenic responses when treated with P-ETC site-specific inhibitors, suggesting a conserved electrogenic pathway. We propose that in cyanobacteria, electrogenic activity may represent a form of overflow metabolism to protect cells under high-intensity light. This study offers insight into electron transfer between phototrophic microorganisms and the environment and expands our knowledge into biologically based mechanisms for harnessing solar energy.


Cyanobacteria Electrogen Electron transfer Microbial fuel cells Photosynthetic 



This research was supported by Elkins Professorship Award to IVB.

Supplementary material

253_2011_3239_Fig7_ESM.jpg (43 kb)
Suppl. Fig. 1

Effect of atrazine on electrogenic activity of Lyngbya (a) or Nostoc (b). Both cultures were dosed first with 25 μM of atrazine (left arrows) followed by an additional 75 μM (right arrows). Periods of illumination or darkness are indicated by white or black bars along x-axis, respectively (JPEG 42 kb)

253_2011_3239_MOESM1_ESM.tif (202 kb)
High resolution image file (TIFF 202 kb)


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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • John M. Pisciotta
    • 1
  • YongJin Zou
    • 1
  • Ilia V. Baskakov
    • 1
    • 2
    Email author
  1. 1.Center for Biomedical Engineering and TechnologyUniversity of Maryland School of MedicineBaltimoreUSA
  2. 2.Department of Anatomy and NeurobiologyUniversity of Maryland School of MedicineBaltimoreUSA

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