Reduction Kinetic of Water Soluble Metal Salts by Geobacter sulfurreducens: Fe2+/Hemes Stabilize and Regulate Electron Flux Rates

• Published in: Frontiers in microbiology 2022-06, Vol.13, p.909109-909109
• Main Authors: Karamash, Maksym, Stumpe, Michael, Dengjel, Jörn, Salgueiro, Carlos A., Giese, Bernd, Fromm, Katharina M.
• Format: Article
• Language: English
• Subjects: bioelectrochemistry; c-cytochrome; Geobacter sulfurreducens; Microbiology; reaction kinetic; remediation
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2022.909109

Geobacter sulfurreducens is a widely applied microorganism for the reduction of toxic metal salts, as an electron source for bioelectrochemical devices, and as a reagent for the synthesis of nanoparticles. In order to understand the influence of metal salts, and of electron transporting, multiheme c -cytochromes on the electron flux during respiration of G. sulfurreducens , the reduction kinetic of Fe 3+ , Co 3+ , V 5+ , Cr 6+ , and Mn 7+ containing complexes were measured. Starting from the resting phase, each G. sulfurreducens cell produced an electron flux of 3.7 × 10 5 electrons per second during the respiration process. Reduction rates were within ± 30% the same for the 6 different metal salts, and reaction kinetics were of zero order. Decrease of c -cytochrome concentrations by downregulation and mutation demonstrated that c -cytochromes stabilized respiration rates by variation of their redox states. Increasing Fe 2+ /heme levels increased electron flux rates, and induced respiration flexibility. The kinetic effects parallel electrochemical results of G. sulfurreducens biofilms on electrodes, and might help to optimize bioelectrochemical devices.