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

GERMÁN DAVID SCHROTT; PABLO SEBASTIÁN BONANNI; LUCIANA ROBUSCHI; JUAN PABLO BUSALMEN

Norwich

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

Biochemical Society

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 cells population to the electrode, but a consensus has not been achieved yet on the relative importance of both contributions. Moreover, external cytochromes have also been called to participate in charge storage when lack of electron acceptor. 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 current profiles have been analyzed all over the growth of biofilms on polarized electrodes to gain information on the role of external cytochromes in charge storage and electron conduction. Modeling work on discharge current data demonstrates that accumulated charge increases along biofilm growth. Chronopotentiometric profiles evidence at least three storing sites with different redox potential. Results support the participation of external cytochromes in electron conduction and charge storage.