CONICET | Buscador de Institutos y Recursos Humanos

Geobacter sulfurreducens is an electrogenic bacteria capable of reducing insoluble electron acceptors. This ability is mainly due to a wide variety of c-type cytochromes (c-Cyts), many of which localized in the extracellular space (Omc c-Cyts), allowing electron transfer beyond the cell limits. Therefore, its study is of great interest: either to elucidate its complex extracellular electron transport chain or for its clear technological potential. In previous studies we observed Omc c-Cyts of G. sulfurreducens form supramolecular complexes. This motivated these work objectives to separate different complexes and evaluate direct electron transfer in and between redox complexes. For this, extracellular proteins were isolated from cultures grown in medium with acetate as electron donor and fumarate as final electron acceptor. Next, we perfomed a hydroxyapatite chromatography and retained proteins were eluted with increasing phosphate buffer concentrations. Protein and c-Cyts contents were estimated by spectrophotometry and SDS gel electrophoresis. We observed the presence of 2 to 7 c-Cyts per elution, which allowed us to infer that different elusions contained different c-Cyts complexes. Altogether, 10 c-Cyts were detected of MW between 80kDa and 15kDa that would include OmcB-C, OmcZ, OmcS and OmcE, previously reported to be involved in external electron transfer. Cyclic voltametry tests enabled us to evaluate different complexes interactions with vitreous carbon electrodes and characterize its elecrochemical response. These results allow us to move forward in the study of multy c-Cyts complexes, their composition and manner of action.