Extracellular polymeric substances are transient media for microbial extracellular electron transfer

Area of Science:

• Microbiology
• Electrochemistry
• Biophysics

Background:

• Microorganisms utilize extracellular electron transfer (EET) for vital processes.
• Extracellular polymeric substances (EPS) surround microbial cells, influencing their interactions.
• Understanding EPS's role in EET is crucial for bioenergy and bioremediation.

Purpose of the Study:

• To investigate the electrochemical activity of EPS in microbial extracellular electron transfer (EET).
• To compare EET in intact and EPS-depleted microbial cells.
• To elucidate the mechanism of electron transfer through EPS.

Main Methods:

• Electrochemical techniques (voltammetry)
• Spectroscopy
• Atomic force microscopy
• Flow cytometry
• Microbiology assays

Main Results:

• EPS depletion altered redox signals from cytochromes and flavins in *Shewanella oneidensis* MR-1.
• EPS itself is electrochemically active, with rate constants suggesting redox species assist EET.
• Electron transfer analysis indicates an electron

Conclusions:

• EPS actively participates in microbial EET.
• Molecular redox species within EPS facilitate electron transfer.
• Electron hopping is the likely mechanism for EET through EPS.