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After discovery of electron transfer from bacteria, most bacteria known to be electrochemically active are utilized as a self-regenerable catalyst at the anode of microbial fuel cells (MFCs). However, the reverse phenomenon, cathodic catalysts is not so widely researched. This present study demonstrated that E. coli O157:H7 was electrochemically active, and it was able to catalyze oxygen reduction at the cathode of bipolar electrode (BPE). Applying a constant potential to the BPE, E. coli O157:H7 can catalyze electrochemical reduction of O 2 , decrease the overpotential of O 2 reduction at the cathode, which in turn generates an electrochemiluminescence (ECL) reporting intensity change at the anode. Significantly, a majority of food matrix does not exhibit catalytic activity for electrochemical reduction of O 2. Meanwhile, due to the physically separation of two poles of closed BPE, complex food matrix at the cathode does not interfere with the ECL reaction at the anode. Therefore, the effect of food matrix is negligible when measuring E. coli O157:H7 levels in food. A low detection limit of 10 CFU mL−1 E. coli O157:H7 could be identified within 1 h. Thus, biocathodes reducing oxygen in BPE-ECL system has shown excellent characteristics in the field of rapid detection of electroactive bacteria in food. [ABSTRACT FROM AUTHOR]

• A temporal sensing platform of Staphylococcus aureus based on Ag@C hybrid BPE are established. • Anodic dissolution can improve sensitivity and extend the detection pattern to the time dimension. • The interference of food matrix can be ignored in this strategy. An Ag@C hybrid bipolar electrode (BPE) sensing platform has been established for the temporal detection of Staphylococcus aureus (S. aureus) in food. Combining the advantages of anodic dissolution of Ag and cathodic biocatalysis of oxygen (O 2) reduction, this strategy showed an ultralow detection limit down to 10 CFU mL−1. As the formation of Ag@C completely quenched the electrochemiluminescence (ECL) emission of luminol, the ECL emission recovery reflected the extent of anodic dissolution. Meanwhile, S. aureus catalyzed the electrochemical reduction of O 2 at the cathode, reducing the overpotential for cathodic O 2 reduction and thus increasing the rate of anodic electron loss, facilitating Ag dissolution and restoring the ECL emission of luminol. When a constant potential was applied, through monitoring the ECL recovery time before and after the incubation of S. aureus on the cathode, S. aureus could be quantified due to the slight difference of the conductivity. [ABSTRACT FROM AUTHOR]

• A functional BPE-ECL platform based on biocathode reducing oxygen was constructed. • Electrochemically active bacteria were able to catalyze oxygen reduction at the cathode of BPE. • A low detection limit of 30 CFU (30 mL system) could be identified within 30 min. A functional bipolar electrode-electrochemiluminescence (BPE-ECL) platform based on biocathode reducing oxygen was constructed for detecting electrochemically active bacteria (EAB) in this paper. Firstly, thiolated trimethylated chitosan quaternary ammonium salt (TMC-SH) layer was assembled on the gold-plated cathode of BPE. TMC-SH contains quaternary ammonium salt branch chain, which can inhibit the growth of microorganisms on the surface or in the surrounding environment while absorbing bacteria. Then, the peristaltic pump was used to flow all of the samples through the cathode, and the EAB was electrostatically adsorbed on the electrode surface. Finally, applying a constant potential to the BPE, bacteria can catalyze electrochemical reduction of O 2 , and decrease the overpotential of O 2 reduction at the cathode, which in turn generates an ECL reporting intensity change at the anode. In this way, live and dead bacteria can be distinguished, and the influence of complex food substrates on detection can be greatly reduced. [ABSTRACT FROM AUTHOR]