title: Nature of the Surface-Exposed Cytochrome-Electrode Interactions in Electroactive Biofilms of Desulfuromonas acetoxidans.
abstract: Metal-respiring bacteria are microorganisms capable of oxidizing organic pollutants present in wastewater and transferring the liberated electrons to an electrode. This ability has led to their application as catalysts in bioelectrochemical systems (BESs), a sustainable technology coupling bioremediation to electricity production. Crucial for the functioning of these BESs is a complex protein architecture consisting of several surface-exposed multiheme proteins, called outer membrane cytochromes, wiring the cell metabolism to the electrode. Although the role of these proteins has been increasingly understood, little is known about the protein-electrode interactions and their impact on the performance of BESs. In this study, we used surface-enhanced resonance Raman spectroscopy in combination with electrochemical techniques to unravel the nature of the protein-electrode interaction for the outer membrane cytochrome OmcB from Desulfuromonas acetoxidans (Dace). Comparing the spectroelectrochemical properties of OmcB bound directly to the electrode surface with those of the same protein embedded inside an electroactive biofilm, we have shown that the surface-exposed cytochromes of Dace biofilms are in direct contact with the electrode surface. Even if direct binding causes protein denaturation, the biofilm possesses the ability to minimize the extent of the damage maximizing the amount of cells in direct electrical communication with the electrode.
authors.affiliation: †Instituto de Tecnologia Quı́mica e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República-Estação Agronómica Nacional, 2780-157 Oeiras, Portugal.
authors.forename: A
authors.initials: A
authors.lastname: Alves
authors.affiliation: ‡Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: H K
authors.initials: HK
authors.lastname: Ly
authors.affiliation: ‡Institut für Chemie, Technische Universität Berlin, Straße des 17. Juni 135, D-10623 Berlin, Germany.
authors.forename: P
authors.initials: P
authors.lastname: Hildebrandt
authors.affiliation: †Instituto de Tecnologia Quı́mica e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República-Estação Agronómica Nacional, 2780-157 Oeiras, Portugal.
authors.forename: R O
authors.initials: RO
authors.lastname: Louro
authors.affiliation: §Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands.
authors.forename: D
authors.initials: D
authors.lastname: Millo
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001674:Bioelectric Energy Sources; D018441:Biofilms; D003580:Cytochromes / Q000378:metabolism*; D045287:Desulfuromonas / Q000502:physiology*; D004566:Electrodes; D013059:Spectrum Analysis, Raman
chemical_list: D001425:Bacterial Outer Membrane Proteins; D003580:Cytochromes; C436968:OmcB protein, bacteria