title: Reduction of low potential electron acceptors requires the CbcL inner membrane cytochrome of Geobacter sulfurreducens.
abstract: The respiration of metals by the bacterium Geobacter sulfurreducens requires electrons generated by metabolism to pass from the interior of the cell to electron acceptors beyond the cell membranes. The G. sulfurreducens inner membrane multiheme c-type cytochrome ImcH is required for respiration to extracellular electron acceptors with redox potentials greater than -0.1 V vs. SHE, but ImcH is not essential for electron transfer to lower potential acceptors. In contrast, deletion of cbcL, encoding an inner membrane protein consisting of b-type and multiheme c-type cytochrome domains, severely affected reduction of low potential electron acceptors such as Fe(III)-oxides and electrodes poised at -0.1 V vs. SHE. Catalytic cyclic voltammetry of a ΔcbcL strain growing on poised electrodes revealed a 50 mV positive shift in driving force required for electron transfer out of the cell. In non-catalytic conditions, low-potential peaks present in wild type biofilms were absent in ∆cbcL mutants. Expression of cbcL in trans increased growth at low redox potential and restored features to cyclic voltammetry. This evidence supports a model where CbcL is a component of a second electron transfer pathway out of the G. sulfurreducens inner membrane that dominates when redox potential is at or below -0.1 V vs. SHE.
authors.affiliation: Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota-Twin Cities, Saint Paul, MN 55108, United States.
authors.forename: Lori
authors.initials: L
authors.lastname: Zacharoff
authors.affiliation: BioTechnology Institute, University of Minnesota-Twin Cities, Saint Paul, MN 55108, United States.
authors.forename: Chi Ho
authors.initials: CH
authors.lastname: Chan
authors.affiliation: BioTechnology Institute, University of Minnesota-Twin Cities, Saint Paul, MN 55108, United States; Department of Microbiology, University of Minnesota-Twin Cities, Saint Paul, MN 55108, United States. Electronic address: dbond@umn.edu.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Bond
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001674:Bioelectric Energy Sources; D018441:Biofilms / Q000254:growth & development; D003580:Cytochromes / Q000235:genetics / Q000378:metabolism*; D004563:Electrochemistry; D004566:Electrodes; D004579:Electron Transport; D005290:Ferric Compounds / Q000378:metabolism; D017353:Gene Deletion; D045302:Geobacter / Q000201:enzymology / Q000378:metabolism*; D017895:Manganese Compounds / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D010087:Oxides / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D003580:Cytochromes; D005290:Ferric Compounds; D017895:Manganese Compounds; D008565:Membrane Proteins; D010087:Oxides; C000499:ferric oxide; C025314:ferric citrate; C027424:manganese oxide
keywords: Cytochrome; Extracellular respiration; Geobacter; Metal reduction; Microbial electrochemical cell