High-resolution electrochemistry of the extracellular electron transfer of Escherichia coli

Escherichia coli is one of the most important model bacteria in microorganism research and is broadly encountered in nature. In the present study, a wild-type E. coli strain K-12 was used for electrochemical investigations. Differential pulse voltammetry showed five pairs of redox peaks both for K-12 cells and the supernatant with potentials (anodic/cathodic) at -0.450/-0.378, -0.125/-0.105, -0.075/-0.055, +0.192/+0.264, and +0.300/+0.414 V (vs. Ag/AgCl), respectively. Chronoamperometry indicates that K-12 cells can produce immediate current by addition of glucose. The current production from K-12 can be 8-fold enhanced by 10.0 M exogenetic vitamin K3, but addition of 10.0 M riboflavin did not enhance the current production. Medium replacement experiments show that 50 % of the K-12 biofilm current was produced via direct extracellular electron transfer pathways. The study provides new insight in the voltammetry of strain K-12 and confirms that E. coli is an electrochemically active bacterium. E. coli has the potential to serve as a model bacterium for studying microbial extracellular electron transfer mechanisms.