External resistance modulates anodic biofilm architecture, electrochemical performance, and EET-related gene expression in Shewanella oneidensis MR-1 microbial fuel cells.
Lower external resistance in microbial fuel cells enhances electrochemical performance and mtrA expression, indicating a trade-off with biofilm accumulation.
Where it sits
this study against the rest of the mazdutide (ibi362) corpusSummary and findings
The study examined the impact of different external resistances on the electrochemical performance and gene expression of Shewanella oneidensis MR-1 biofilms in microbial fuel cells. A resistance of 10 Ω resulted in the highest power density and up-regulation of mtrA. Higher resistances led to thicker biofilms but reduced electrochemical output.
Abstract
External resistance is a key operational variable in microbial fuel cells (MFCs), yet its mechanistic influence on pure-culture electrogenic biofilms remains incompletely understood. Here, we investigated how fixed external resistances (10, 100, 500, and 1000 Ω) applied during start-up modulate electrochemical performance, architecture, membrane-integrity-associated viability, and extracellular electron transfer (EET)-related gene expression in Shewanella oneidensis MR-1 anodic biofilms. After 10 days in dual-chamber MFCs, polarization analysis, cyclic voltammetry, confocal microscopy with LIVE/DEAD staining, epifluorescence viable-cell counting, and reverse-transcription quantitative PCR targeting mtrA and omcA were performed. Low resistance (10 Ω) produced the highest maximum power density (130 mW m<sup>-2</sup>), current density at maximum power (1609.6 mA m<sup>-2</sup>), lowest apparent internal resistance, strongest anodic redox activity, and significant mtrA up-regulation. In contrast, intermediate and high resistances promoted thicker biofilms with higher membrane-integrity-associated live signal but lower electrochemical output. omcA expression was not significantly affected. Multivariate correlation and regression analyses identified anodic peak current, peak potential, and external resistance as the main predictors of maximum power density (R<sup>2</sup> = 0.978), indicating that external resistance modulates a trade-off between biofilm accumulation and electrochemical output, with mtrA acting as a molecular marker of the anodic electroactive state.
Background
This study addresses the influence of external resistance on the performance of microbial fuel cells (MFCs), specifically focusing on the electrogenic biofilms of Shewanella oneidensis MR-1. Previous research has established the importance of external resistance in MFCs, but the detailed mechanisms affecting biofilm architecture and gene expression remain unclear. Understanding these mechanisms is crucial for optimizing MFC performance.
Methods
The researchers used dual-chamber MFCs with Shewanella oneidensis MR-1 biofilms and applied fixed external resistances of 10, 100, 500, and 1000 Ω during start-up. Over 10 days, they conducted polarization analysis, cyclic voltammetry, and confocal microscopy with LIVE/DEAD staining. Epifluorescence viable-cell counting and reverse-transcription quantitative PCR targeting mtrA and omcA were also performed.
Results
At 10 Ω resistance, the biofilms exhibited the highest maximum power density of 130 mW m^-2 and a current density of 1609.6 mA m^-2. This condition also showed significant up-regulation of the mtrA gene. Higher resistances resulted in thicker biofilms with higher membrane integrity but lower electrochemical output. The expression of omcA was not significantly affected by resistance levels.
Interpretation
The findings suggest that lower external resistance enhances electrochemical performance and mtrA expression in Shewanella oneidensis MR-1 biofilms, while higher resistances favor biofilm thickness and viability. The study highlights a trade-off between biofilm accumulation and electrochemical output, with mtrA serving as a potential marker for anodic electroactivity. These results align with previous studies on the importance of resistance in MFCs but provide new insights into gene expression dynamics.
Key findings
- Maximum power density of 130 mW m^-2 at 10 Ω.
- Current density at maximum power was 1609.6 mA m^-2 at 10 Ω.
- Significant up-regulation of mtrA at 10 Ω.
- omcA expression was not significantly affected.
- R^2 = 0.978 for predictors of maximum power density.
Limitations
- Study limited to Shewanella oneidensis MR-1.
- Focus on microbial fuel cells may not generalize to other systems.
- Short 10-day observation period.