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

Abstract

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 +0.04 V 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)6Cl3 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.

Scanning Probe Microscopy for Nanoscale Electrochemical Imaging

“…The constant-height mode SECM measurements of the patterned cells enabled mapping of the activity of ATP-binding cassette transporters . SECM was applied for real-time characterization of the dynamic formation process of a biofilm of Shewanella oneidensis MR-1 on an electrode by monitoring the redox mediator current of Ru­(NH 3 ) 6 Cl 3 …”

Bacterial Biofilm Probed by Scanning Electrochemical Microscopy: A Review

“…Hsing et al reported a dynamic formation process of S. oneidensis biofilms on electrodes using SECM. [24] Figure 4a showed the SECM area scan results presenting a 3D configure corresponding to the edge of biofilm. They also compared the time-lapse approach curves after 2 hr, 25 hr, and 35 hr of the electrogenic experiment, which indicated that the growing bacterial film hindered electron transfer and led to a current decrease.…”

Biological imaging with scanning electrochemical microscopy

“…Though most of the work dealt with inspections of eukaryotic cells from vertebrates as the more common biological model case, bio-SECM on fungal eukaryotic cells and bacterial prokaryotic cells has been carried out as well. In the context of the development of biofuel cells, the transmembrane charge transfer ability of eukaryotic yeast cells was, for instance, assessed by means of G/C SECM [65,66] colonies [67], quorum sensing of aggregates of Pseudomonas aeruginosa [68] and metabolite production of Pseudomonas aeruginosa during proliferation [69] are examples of G/C-SECM studies with bacterial prokaryotes. Exotic targets for biological SECM studies were salt glands on the leaf of the halophyte Cynodon dactylon (L.) [70] and chloroplasts and their thylakoid membranes for which local photosynthetic flux measurements have been attempted [71].…”