Feedback current production by a ferrous mediator revealing the redox properties of Shewanella oneidensis MR-1

Abstract

• FcMeOH mediated electron transfer between Shewanella cells and electrodes. • A positive feedback current demonstrates that electron may transfer among cells. • Cyclic voltammetry reveals redox properties of S. oneidensis MR-1. • Electrons may transfer by spreading among redox flavocytochromes. The redox properties of electroactive bacteria play an important role in biogeochemical cycling, environmental remediation and bioenergy generation. But the detailed mechanisms on the redox properties of living cells are still vague. Herein, we designed a series of electrochemical tests mediated by FcMeOH to investigate the bacterial electrode process. Cyclic voltammograms and a positive feedback current production of scanning electrochemical microscopy provided evidence on the process of electrochemical oxidation followed by biocatalytic reduction. Moreover, an irreversible process for the redox behaviours of Shewanella oneidensis MR-1 revealed that electrons may transfer by spreading among redox flavocytochromes at the cell membrane and that these proteins may form a conductive network to perpetuate cathodic electron transfer. These results provide an insight into redox reactions at the microbe-electrode interface.