Extracellular electron transfer

The physiological and biogeochemical phenomenon by which microbes move electrons across their outer membrane to acceptors outside the cell — enabling mineral (metal-oxide) reduction, current generation in microbial fuel cells, and sediment-scale redox coupling. It is the umbrella under which several distinct conduction mechanisms sit, and matters to this vault as the concept that bridges its otherwise-separate electromicrobiology notes: the contested Geobacter nanowire (heme-based cytochrome polymers vs. conductive pili) and the cable-bacteria wire (a non-redox, metal-like sulfur-ligated nickel cofactor). Different organisms, different physics, same problem — getting an electron out of a cell and somewhere useful.

References

• claim-geobacter-conductive-filaments-are-omcs-cytochrome-polymers
• claim-lovley-2005-proposed-geobacter-nanowires-are-conductive-pili
• claim-geobacter-pili-are-secretory-pseudopili-not-nanowires
• claim-cable-bacteria-conduct-through-nickel-protein-wire
• claim-spectral-induced-polarization-detects-bacterial-cells-in-sand (geophysical detection of microbial electrical activity)

Updates

• 2026-08-07: the Geobacter cytochrome-nanowire dispute now has a computed-physics prong — a Marcus-theory upper bound on redox-hopping current (~0.14 pA/filament) that the measured conductivities exceed by 10²–10⁵-fold, with the critic affirming the cytochrome identity and locating the open problem in the measurement technique (claim-guberman-pfeffer-0-14-pa-ceiling-is-computed-not-measured, claim-guberman-pfeffer-blames-measurement-not-cytochrome-identity). New hub for the mechanism the dispute turns on: entity-redox-hopping.