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Yavarinasab, Adel

University of British Columbia

The main goal of this thesis is to apply electrochemical techniques, with a focus on electrochemical impedance spectroscopy, to improve our understanding of different aspects of bacterial physiology, specifically electrochemistry of biofilm and production of specific metabolites from intestinal bacteria. We first analyzed the electron transfer properties of biofilms, which are crucial for nutrient cycling and bacterial pathogenesis in the model organism Bacillus subtilis. We used interdigitated gold electrodes to measure the electrochemical activity of biofilm-forming B. subtilis and biofilm-deficient mutants over three days. Chronoamperometry and cyclic voltammetry revealed current fluctuations and significant differences in voltammograms, likely due to redox-active molecules present only in the biofilm-forming cells. Additionally, electrochemical impedance spectroscopy identified charge transfer resistance exclusively in biofilm-forming cells. Finally, by using confocal microscopy, we identified a correlation between gene expression in biofilm matrix formation genes and charge transfer. These findings highlight the temporal relationship between biofilm-associated electrochemical activity and gene expression. We were able to offer a novel method, real-time electrochemical impedance spectroscopy, for detecting biofilm-related electrochemical processes. The second topic of this work is the development of an electrochemical sensor for real-time, quantitative, and direct measurement of short-chain fatty acids (SCFAs), as key metabolites produced by gut bacteria. The sensor, made by depositing ZnO and polyvinyl alcohol on a gold electrode, detects acetic acid, propionic acid, and butyric acid at concentrations from 0.5 to 20 mg/ml. The sensor demonstrated its ability to measure SCFAs in the liquid phase at room temperature, unlike previous sensors that required gas-phase detection. Impedance measurements were also used to analyze the sensor's performance in complex media, showing accurate measurements across a range of 0.5 to 10 mg/ml SCFA concentrations. The sensor's Faradaic responses were utilized to develop a model for screening bacterial isolates, identifying those that secrete SCFAs in vitro. This sensor provides a stable, sensitive, and miniaturized method for real-time monitoring of SCFA levels in complex biological samples, offering a fast and non-destructive diagnostic tool. In conclusion, this thesis enhances our understanding of bacterial physiology by applying electrochemical techniques and offering valuable tools for precise monitoring of microbial activity and metabolism.

Text

2025-04-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/90751

Biomedical Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/