Low electrode potentials enhance current generation by Geobacter sulfurreducens biofilms: A high-throughput study.

Area of Science:

• Electromicrobiology
• Microbial electrochemistry
• Bioenergetics

Background:

• Geobacter sulfurreducens utilizes diverse extracellular electron transfer (EET) pathways influenced by electron acceptor potential.
• Complete understanding of EET mechanisms and the effects of limiting potentials is lacking.

Purpose of the Study:

• Investigate the impact of a wide range of potentials ([-0.25 to 0] V vs. SHE) on Geobacter sulfurreducens electroactive biofilms (EABs).
• Characterize metabolic energy generation and EET mechanisms under varying thermodynamic conditions.

Main Methods:

• Utilized a custom high-throughput system for 128 parallel experiments.
• Grew axenic G. sulfurreducens EABs for 500 hours across three stages.
• Performed electrochemical characterization to analyze biofilm performance.

Main Results:

• EABs grown at potentials below the midpoint potential ([-0.18 to -0.16] V) showed slower growth, 50% smaller biofilm size, and 2.4-fold higher anodic plateau currents compared to those at 0 V.
• Lower potential growth resulted in enhanced charge transport and significantly higher charge carrier concentrations ([1.6 vs. 0.4] mM_e).
• Charge carrier concentration linearly correlated with anodic plateau current; low-potential redox pools constituted 50%-70% of storable charge.

Conclusions:

• Lower potentials induce overexpression of charge carriers in G. sulfurreducens EABs.
• High-throughput methodologies are valuable for advancing electromicrobiology research.
• Findings provide insights into EET regulation under thermodynamically challenging conditions.