During extracellular electron transfer, Geobacter sulfurreducens constitutively expresses the bc-cytochrome CbcL, yet cells containing only this menaquinone oxidase fail to respire above −0.1 V vs. SHE. By identifying mutations within cbcL that permit growth at higher potentials, we provide evidence that this cytochrome is regulated by redox potential. Strains expressing only CbcLV205A, CbcLV205G, and CbcLF525Y were capable of growth with high potential electron acceptors including Fe(III) citrate, Mn(IV) oxides, and electrodes poised at +0.1 V vs. SHE. Electrochemical characterization of wild type CbcL revealed oxidative inactivation of electron transfer above −0.1 V, while CbcLV205A, CbcLV205G, and CbcLF525Y remained active. Growth yields of CbcLV205A, CbcLV205G, and CbcLF525Y were only 50 % of WT, consistent with CbcL-dependent electron transfer conserving less energy. These data support the hypothesis that CbcL has evolved to rapidly shut off in response to redox potential, in order to divert electrons to higher yield oxidases that coexist in the Geobacter membrane.
|Original language||English (US)|
|State||Published - Feb 13 2023|
Bibliographical notePublisher Copyright:
© 2022 The Authors. ChemElectroChem published by Wiley-VCH GmbH.
- amino acid substitution
- c-type cytochrome
- extracellular electron transfer