IMR Press / FBL / Volume 27 / Issue 6 / DOI: 10.31083/j.fbl2706174
Open Access Review
Molecular Mechanisms of Microbial Extracellular Electron Transfer: The Importance of Multiheme Cytochromes
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1 Institute of Chemical and Biological Technology António Xavier (ITQB NOVA), NOVA University Lisbon, 2780-157 Oeiras, Portugal
2 Associate Laboratory i4HB – Institute for Health and Bioeconomy, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
3 UCIBIO – Applied Molecular Biosciences Unit, Chemistry Department, NOVA School of Science and Technology, NOVA University Lisbon, 2829-516 Caparica, Portugal
*Correspondence: (Catarina M. Paquete)
Academic Editor: Rosa Alduina
Front. Biosci. (Landmark Ed) 2022, 27(6), 174;
Submitted: 14 March 2022 | Revised: 28 April 2022 | Accepted: 11 May 2022 | Published: 1 June 2022
(This article belongs to the Special Issue Fundamental Aspects of Extracellular Electron Transfer Processes)
Copyright: © 2022 The Author(s). Published by IMR Press.
This is an open access article under the CC BY 4.0 license.

Extracellular electron transfer is a key metabolic process of many organisms that enables them to exchange electrons with extracellular electron donors/acceptors. The discovery of organisms with these abilities and the understanding of their electron transfer processes has become a priority for the scientific and industrial community, given the growing interest on the use of these organisms in sustainable biotechnological processes. For example, in bioelectrochemical systems electrochemical active organisms can exchange electrons with an electrode, allowing the production of energy and added-value compounds, among other processes. In these systems, electrochemical active organisms exchange electrons with an electrode through direct or indirect mechanisms, using, in most cases, multiheme cytochromes. In numerous electroactive organisms, these proteins form a conductive pathway that allows electrons produced from cellular metabolism to be transferred across the cell surface for the reduction of an electrode, or vice-versa. Here, the mechanisms by which the most promising electroactive bacteria perform extracellular electron transfer will be reviewed, emphasizing the proteins involved in these pathways. The ability of some of the organisms to perform bidirectional electron transfer and the pathways used will also be highlighted.

extracellular electron transfer
bioelectrochemical systems
biogeochemical cycling of elements
electroactive organisms
reduction potential
multiheme cytochromes
Fig. 1.
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