Electrochemical Catalysis of Inorganic Complex K₄[Fe(CN)₆] by Shewanellaoneidensis MR-1

The interaction between metal and bacteria is a universal and important biogeochemical processin environment. As a dissimilatory metal reduction bacterium, the electrochemically activebacteriium Shewanella oneidensis MR-1 can transfer intracellular electrons to minerals. This ability is attributed to the redox proteins localized on the outer-membrane, for example, the MtrC, MtrB, MtrA and CymA². Here we investigate its electrochemical properties towards redoxinorganic redox compounds. It shows strong electrocatalysis toward electrochemical oxidation of K₄[Fe(CN)₆]. As a redox molecule, K₄[Fe(CN)₆] gives a pair of redox peaks on voltammetry on bare glassy carbon electrode (GCE), symmetric with ideal peak-peak separation of about 60 mV, indicating ofa reversible one-electron transfer process(blue curve, Figure 1). Surprisingly, the presence of S. oneidensis MR-1 on GCE results an asymmetric redox peak, with almost disappearance of the cathodic peak and strengthen of the anodic peak, which is a typical catalysis feature of electrochemical oxidation. Further experiments show that S. oneidensis MR-1 does not give such electrocatalysis toredox compounds such as Ru[(NH₃)₆]Cl₃and Resorufin. Selectivity andelectrocatalysis mechanisms of S. oneidensis MR-1 are under investigation. The ability of S. oneidensis MR-1 to catalyze redoxaction of inorganic metal complex compounds will provide an insight on metal cycles in nature.