title: Cation-limited kinetic model for microbial extracellular electron transport via an outer membrane cytochromeCcomplex.
abstract: Outer-membranec-type cytochrome (OMc-Cyt) complexes in several genera of iron-reducing bacteria, such asShewanellaandGeobacter, are capable of transporting electrons from the cell interior to extracellular solids as a terminal step of anaerobic respiration. The kinetics of this electron transport has implications for controlling the rate of microbial electron transport during bioenergy or biochemical production, iron corrosion, and natural mineral cycling. Herein, we review the findings fromin-vivoandin-vitrostudies examining electron transport kinetics through single OMc-Cyt complexes inShewanella oneidensisMR-1.In-vitroelectron flux via a purified OMc-Cyt complex, comprised of MtrA, B, and C proteins fromS. oneidensisMR-1, embedded in a proteoliposome system is reported to be 10- to 100-fold faster compared within-vivoestimates based on measurements of electron flux per cell and OMc-Cyts density. As the proteoliposome system is estimated to have 10-fold higher cation flux via potassium channels than electrons, we speculate that the slower rate of electron-coupled cation transport across the OM is responsible for the significantly lower electron transport rate that is observedin-vivo. As most studies to date have primarily focused on the energetics or kinetics of interheme electron hopping in OMc-Cyts in this microbial electron transport mechanism, the proposed model involving cation transport provides new insight into the rate detemining step of EET, as well as the role of self-secreted flavin molecules bound to OMc-Cyt and proton management for energy conservation and production inS. oneidensisMR-1.
authors.affiliation: Global Research Center for Environment and Energy based on Nanomaterials Science (GREEN), National Institute for Materials Science (NIMS), Tsukuba, Ibaraki 305-0044, Japan; Department of Applied Chemistry, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Okamoto
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Tokunou
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Junki
authors.initials: J
authors.lastname: Saito
keywords: Shewanella oneidensis MR-1; electrochemistry; flavin; iron-reducing bacteira; proton motive force