Real-Time Label-Free Monitoring of Shewanella oneidensis MR-1 Biofilm Formation on Electrode During Bacterial Electrogenesis Using Scanning Electrochemical Microscopy

Formation of biofilm on an electrode surface is usually a prerequisite for efficient electron transfer from electrogenic bacteria onto electrode, and the geometric status of the biofilm governs the generated current. In this study, we propose a real-time characterization method to track the dynamic formation process of biofilm on electrode using scanning electrochemical microscopy (SECM). Shewanella oneidensis MR-1 was chosen in this work as an electrogenic model species. A plane electrode at the bottom of a electrochemical cell filled with bacteria suspension was biased at +0.04V vs. Ag/AgCl as the sole electron acceptor under anaerobic environment, while a movable ultramicroelectrode (UME) was employed to track the localized faradaic current generated by a redox mediator, Ru(NH3)(6)Cl-3 above the bottom electrode. The growth rate of biofilm showed some spatial heterogeneity, which might be explained by inhomogeneous mass transfer and non-uniformity of electrode surface. The application of SECM into bacterial electrogenesis studies offered a simple and label-free monitoring method to evaluate the bacteria-electrode coupling status.