New evidences on the role of external cytochromes in current gating and electron storage

SCHROTT GERMÁN D.; BONANNI P. SEBASTIAN; ROBUSCHI LUCIANA; BUSALMEN JUAN PABLO

Norwich

Congreso; Electron transfer at the microbe-mineral interface; 2012

Biochemical Society of the United Kingdom

G. sulfurreducens can grow on polarized electrodes and produce thick biofilms of more than 50 µm using the electrode as sole electron acceptor. It is currently accepted that this strain make use of external cytochromes to contact to the electrode. External cytochromes and putatively conductive pili give support to alternative models of electron conduction from the whole population to the electrode, but a consensus has not yet been achieved on the relative importance of both contributions. Moreover, external cytochromes have also been called to participate in charge storage in the lack of electron acceptors. Charge accumulation on biofilm grown on electrodes drive the open circuit potential to negative values. Interestingly, accumulated charge can be recovered upon repolarization. In this work transient potential and discharge current profiles have been obtained all over the growth of biofilms on polarized electrodes. Discharge current data evidence a rapid stabilization of the biofilm/electrode interface by the beginning of the exponential growth. After that, charge accumulated into the biofilm increases in relation to the biofilm current output, as demonstrated by modeling work. Chronopotentiometric profiles evidence at least three kind of charge storing sites with different redox potential, two of which agree with redox signals in the biofilm voltammetric profile. Presented results support the participation of external cytochromes in both, electron conduction and charge storage.