title: Cell-secreted flavins bound to membrane cytochromes dictate electron transfer reactions to surfaces with diverse charge and pH.
abstract: The variety of solid surfaces to and from which microbes can deliver electrons by extracellular electron transport (EET) processes via outer-membrane c-type cytochromes (OM c-Cyts) expands the importance of microbial respiration in natural environments and industrial applications. Here, we demonstrate that the bifurcated EET pathway of OM c-Cyts sustains the diversity of the EET surface in Shewanella oneidensis MR-1 via specific binding with cell-secreted flavin mononucleotide (FMN) and riboflavin (RF). Microbial current production and whole-cell differential pulse voltammetry revealed that RF and FMN enhance EET as bound cofactors in a similar manner. Conversely, FMN and RF were clearly differentiated in the EET enhancement by gene-deletion of OM c-Cyts and the dependency of the electrode potential and pH. These results indicate that RF and FMN have specific binding sites in OM c-Cyts and highlight the potential roles of these flavin-cytochrome complexes in controlling the rate of electron transfer to surfaces with diverse potential and pH.
authors.affiliation: 1] Departments of Earth Sciences and Biological Sciences, University of Southern California, Los Angeles, CA 90089 [2] Department of Applied Chemistry, University of Tokyo, Bunkyo-ku, Tokyo, 113-8654.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Okamoto
authors.affiliation: Department of Applied Chemistry, University of Tokyo, Bunkyo-ku, Tokyo, 113-8654.
authors.forename: Shafeer
authors.initials: S
authors.lastname: Kalathil
authors.affiliation: Department of Applied Chemistry, University of Tokyo, Bunkyo-ku, Tokyo, 113-8654.
authors.forename: Xiao
authors.initials: X
authors.lastname: Deng
authors.affiliation: Department of Applied Chemistry, University of Tokyo, Bunkyo-ku, Tokyo, 113-8654.
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Hashimoto
authors.affiliation: Biofunctional Catalyst Research Team, RIKEN Center for Sustainable Resource Science, Wako, Saitama 351-0198, Japan.
authors.forename: Ryuhei
authors.initials: R
authors.lastname: Nakamura
authors.affiliation: 1] Departments of Earth Sciences and Biological Sciences, University of Southern California, Los Angeles, CA 90089 [2] J. Craig Venter Institute, San Diego, CA 92121.
authors.forename: Kenneth H
authors.initials: KH
authors.lastname: Nealson
mesh_terms: D001665:Binding Sites; D003574:Cytochrome c Group / Q000378:metabolism*; D004579:Electron Transport / Q000502:physiology*; D004583:Electrons; D005486:Flavin Mononucleotide / Q000378:metabolism; D005415:Flavins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008566:Membranes / Q000378:metabolism*; D012256:Riboflavin / Q000378:metabolism; D020592:Shewanella / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; D005415:Flavins; D005486:Flavin Mononucleotide; D012256:Riboflavin