Long-distance electron transfer by G. sulfurreducens biofilms results in accumulation of reduced c-type cytochromes.
Bottom Line: So close, but yet so far: G. sulfurreducens c-type cytochromes become reduced as biofilms grow on electrodes beyond a few cell thicknesses, even if the electrode is poised well above the potential required to oxidize all cytochromes.Cytochrome redox state also lags behind rapid potential changes during voltammetry, but only when the films are multiple cell layers thick, as would be expected if diffusional or exchange-based kinetics controls electron transfer between cytochromes.
Affiliation: BioTechnology Institute and Department of Microbiology, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Ave St. Paul MN 55108, USA.Show MeSH
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Mentions: For thin biofilms, the oxidation state of c-type cytochromes remained a function of imposed potential, even when scan rates were increased (Figure 5 A and B). At scan rates of 20 mV s−1, no significant hysteresis or deviation was detected. By plotting the derivative of the redox profile, only a slight flattening of the response was evident, but both forward and reverse scans remained centered on the same midpoint potential. These observations were consistent with all steps in electron transfer being rapid enough to bring all cytochromes to the same potential as the electrode, even when the potential was changed 40-fold faster.
Affiliation: BioTechnology Institute and Department of Microbiology, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Ave St. Paul MN 55108, USA.