title: pH, redox potential and local biofilm potential microenvironments within Geobacter sulfurreducens biofilms and their roles in electron transfer.
abstract: The limitation of pH inside electrode-respiring biofilms is a well-known concept. However, little is known about how pH and redox potential are affected by increasing current inside biofilms respiring on electrodes. Quantifying the variations in pH and redox potential with increasing current is needed to determine how electron transfer is tied to proton transfer within the biofilm. In this research, we quantified pH and redox potential variations in electrode-respiring Geobacter sulfurreducens biofilms as a function of respiration rates, measured as current. We also characterized pH and redox potential at the counter electrode. We concluded that (1) pH continued to decrease in the biofilm through different growth phases, showing that the pH is not always a limiting factor in a biofilm and (2) decreasing pH and increasing redox potential at the biofilm electrode were associated only with the biofilm, demonstrating that G. sulfurreducens biofilms respire in a unique internal environment. Redox potential inside the biofilm was also compared to the local biofilm potential measured by a graphite microelectrode, where the tip of the microelectrode was allowed to acclimatize inside the biofilm.
authors.affiliation: The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, PO Box 642710, Pullman, Washington 99164-2710, USA.
authors.forename: Jerome T
authors.initials: JT
authors.lastname: Babauta
authors.forename: Hung Duc
authors.initials: HD
authors.lastname: Nguyen
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Harrington
authors.forename: Ryan
authors.initials: R
authors.lastname: Renslow
authors.forename: Haluk
authors.initials: H
authors.lastname: Beyenal
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D003470:Culture Media / Q000737:chemistry; D004566:Electrodes / Q000382:microbiology*; D004579:Electron Transport; D045302:Geobacter / Q000378:metabolism / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D010084:Oxidation-Reduction
chemical_list: D003470:Culture Media