Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
. 2025 Jul 16:13:1621274.
doi: 10.3389/fchem.2025.1621274. eCollection 2025.

Electron transport across the cell envelope via multiheme c-type cytochromes in Geobacter sulfurreducens

Media Zakizadeh Tabari  1 , Allon I Hochbaum  2
Affiliations
Review

Electron transport across the cell envelope via multiheme c-type cytochromes in Geobacter sulfurreducens

Media Zakizadeh Tabari et al. Front Chem. .

Abstract

Extracellular electron transfer (EET) enables certain microorganisms to respire using soluble and insoluble extracellular electron acceptors by transporting electrons across the cell envelope. Among these, G. sulfurreducens serves as a model organism for understanding direct EET pathways, where multiheme c-type cytochromes mediate electron transport from intracellular redox carriers to extracellular acceptors such as Fe(III) oxides and electrodes. This review focuses on heme-dependent electron transfer in Geobacter sulfurreducens, detailing the roles of inner membrane cytochromes, periplasmic carriers, outer membrane conduits, and recently characterized extracellular nanowires formed by polymerized multiheme c-type cytochromes, including OmcS, OmcE, and OmcZ. We examine the state of understanding of their physiological function, their structural features, expression patterns, and essentiality under various respiratory conditions. These insights advance our understanding of microbial anaerobic respiration and have implications for biogeochemical cycling, bioenergy generation, and bioremediation. The molecular architecture, assembly mechanisms, and secretion pathways of multiheme c-type cytochrome nanowires remain active areas of investigation, offering promising directions for future research and biotechnological innovation in engineered microbial systems.

Keywords: cytochrome nanowire; electron transport; extracellular electron transfer; geobacter sulfurreducens; outer membrane cytochromes.

PubMed Disclaimer

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
All (c-cyts) and multiheme (MHCs) c-type cytochromes as a fraction of total unique proteins encoded in the G. sulfurreducens genome as compared to other organisms. Inset: number of MHCs in G. sulfurreducens and other model organisms. Proteomes were downloaded June 2025 from UniProt (proteome ID Gs: UP000000577; Ec: UP000000625 Sc: UP000002311; Hs: UP000005640).
FIGURE 2
FIGURE 2
Components of the electron transfer pathway in G. sulfurreducens, from intracellular acetate oxidation to outer membrane and extracellular cytochromes. IM = inner membrane, P = periplasm, OM = outer membrane.
See this image and copyright information in PMC

Comment in

References

    1. Adhikari R. Y., Malvankar N. S., Tuominen M. T., Lovley D. R. (2016). Conductivity of individual Geobacter pili. RSC Adv. 6, 8354–8357. 10.1039/C5RA28092C - DOI
    1. Aklujkar M., Coppi M. V., Leang C., Kim B. C., Chavan M., Perpetua L., et al. (2013). Proteins involved in electron transfer to Fe (III) and Mn (IV) oxides by Geobacter sulfurreducens and Geobacter uraniireducens . Microbiology 159, 515–535. 10.1099/mic.0.064089-0 - DOI - PubMed
    1. Ammend M., Chan C. H., Bond D. R. (2023). Genetic evidence that multiple cytochrome nanowires are necessary for Fe(III) oxide reduction in Geobacter sulfurreducens . ARPHA Conf. Abstr. 6, e108028. 10.3897/aca.6.e108028 - DOI
    1. Antunes J. M. A., Silva M. A., Salgueiro C. A., Morgado L. (2022). Electron flow from the inner membrane towards the cell exterior in Geobacter sulfurreducens: biochemical characterization of cytochrome CbcL. Front. Microbiol. 13, 898015. 10.3389/fmicb.2022.898015 - DOI - PMC - PubMed
    1. Ayako K., Takahiro T., Takashi F., Yoshihiro K., Toshiyuki U., Miyuki N., et al. (2021). Proteolytic maturation of the outer membrane c-type cytochrome OmcZ by a subtilisin-like serine protease is essential for optimal current production by Geobacter sulfurreducens . Appl. Environ. Microbiol. 87, e02617–e02620. 10.1128/AEM.02617-20 - DOI - PMC - PubMed

LinkOut - more resources