Plasmonic Probing Single-Cell Bio-Current Waves with a Shrinking Magnetite Nanoprobe.

Area of Science:

• Microbiology
• Electrochemistry
• Nanotechnology

Background:

• Microbial fuel cells (MFCs) show limited output current, hindering practical applications.
• Previous research focused on external factors to enhance bacterial charge extraction efficiency.
• Understanding intracellular mechanisms is crucial for improving MFC performance.

Purpose of the Study:

• To investigate intracellular factors limiting extracellular electron transfer in single microbial cells.
• To correlate intracellular processes with bio-current generation and output.
• To explain the discrepancy between single-cell and population-level current outputs in MFCs.

Main Methods:

• Utilized plasmonic imaging to monitor the shrinking kinetics of a single magnetite nanoprobe.
• Immobilized nanoprobes on single *Shewanella oneidensis* MR-1 cells to track respiratory-driven processes.
• Simultaneously traced endogenous cellular oscillations to identify correlations with bio-current.

Main Results:

• Quantified nanoprobe dissolution revealed previously undescribed bio-current fluctuations (0–2.7 fA) on a ~40 min cycle.
• Bio-current waves were correlated with periodic cellular electrokinesis.
• Unsynchronized electron transfer in cell populations resulted in a mean current of 0.24 fA/cell, lower than single-cell measurements.

Conclusions:

• Intracellular electrokinetic oscillations dictate single-cell extracellular electron transfer limits.
• Population-level unsynchronized activity explains lower average MFC output compared to single-cell potential.
• Enhancing MFC power output may involve extending the active episodes of intracellular bio-current waves.