Conductance and Capacitance of Electrode-Respiring Geobacter Sulfurreducens Biofilms Using a Quartz Crystal Microbalance and Electrochemical Impedance Spectroscopy

Abstract

Model electrochemically active bacteria such as Geobacter sulfurreducens are well-established and are often used to study microbial interactions within biofilms that transfer electrons to electrodes. In the presented work, we utilized a quartz crystal microbalance (QCM) coupled to electrochemical impedance spectroscopy (EIS) to simultaneously monitor biofilm growth and the microbial interaction with the electrode. The QCM monitored the frequency shift from the background resonant frequency in real time while the current increased because of biofilm growth. At select times during biofilm growth, we halted the current and obtained biofilm impedance spectra. The short-term and long-term electrode interactions of G. sulfurreducens biofilms were demonstrated. In the short-term, the frequency shift was linear with respect to current for the biofilm. In long-term biofilm growth up to the exponential phase, a second linear region was observed. Biofilm impedance spectra taken across these times revealed a reproducible electrochemical signal. Conductance of the biofilm was linear with current whereas capacitance reached a limiting value towards the end of exponential growth. We show that a simple iV relationship can explain the linear behavior of conductance and current. Capacitance could be used to identify the transition between different growth phases. We compare the biofilm response on the QCM to capacitive, electrochemically-deposited polyaniline films. Our results suggest that the QCM can be used in applications where it is beneficial to identify electrochemically active bacteria that form efficient current-producing biofilms.

Key findings

• ▸The QCM monitored the frequency shift from the background resonant frequency in real time while the current increased because of biofilm growth.
• ▸sulfurreducens biofilms were demonstrated.
• ▸Conductance of the biofilm was linear with current whereas capacitance reached a limiting value towards the end of exponential growth.

Keywords

Identifiers

DOI

10.1149/ma2016-01/36/1814

Journal

ECS Meeting Abstracts

Year

2016