Conductive pili

Biofuel cells — Figure. Schematic illustration of identified electron transfer mechanisms in microbial fuel cells. Electron transfer via (a) cell membrane-bound cytochromes, (b) electrically conductive pili (nanowires), (c) microbial redox mediators, and (d) via oxidation of reduced secondary metabolites [v]... 

As the cell membrane of microorganisms is non-conductive, how to transfer the electrons across the cell membrane (usually termed as extracellular electron transfer (EET)) is the key issue for MES. Eor the bioanode, extracellular electron transfer usually refers to outwards electron transfer, which is related to transportation of intracellular electrons to the solid electrode. To date, at least three electron transfer pathways have been explored, i.e., electron shuttle mediated electron transfer, outer membrane redox proteins mediated contact-based electron transfer, and conductive pili mediated electron transfer (Figure 5.5). ... 

DET - electrically conductive pili form a physical connection between the microorganisms and the substrates [19, 22, 23]. 

Microbial Electrosynthesis, Fig. 2 (a) Electron trans- pathway via multiheme proteins in Shewanella oneidensis fer pathway via multiheme proteins and conductive pili in (for further details, see text)... 

Cologgi DL, Lampa-Pastirk S, Speers AM, Kelly SD, Reguera G (2011) Extracellular reduction of uranium via Geobacter conductive pili as a protective cellular mechanism. Proc Natl Acad Sci 108(37) 15248-15252... 

Figure 9.2. Mechanisms of EET (a) Electron transfer through use of redox mediator. Mediator is reduced by bacterium and subsequently oxidized by electrode. Use of mediator to transfer electrons to other bacteria may be possible, (b) Electron transfer through outer membrane c-type cytochromes. Electrons are transferred through outer membrane proteins in direct contact with electrode, (c) Electron transfer through use of microbial nano-wires. Conductive pili confer conductivity to the bio film allowing electron transfer to other bacteria as well as electrode transfer of electrons from nano-wires to electrodes likely catalyzed by c-type cytochromes dispersed in the biofilm.

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