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Multiheme Cytochromes and the Bacterial Nanowires of Shewanella oneidensis MR-1: Regulation, Structure, and Extracellular Electron Transport Mechanisms

Pirbadian, Sahand and Barchinger, Sarah E. and Subramanian, Poorna and Sambles, Christine M. and Baker, Carol S. and Burroughs, Nigel J. and Jensen, Grant J. and Golbeck, John H. and El-Naggar, Mohamed Y. (2016) Multiheme Cytochromes and the Bacterial Nanowires of Shewanella oneidensis MR-1: Regulation, Structure, and Extracellular Electron Transport Mechanisms. Biophysical Journal, 110 (3). 314A. ISSN 0006-3495. http://resolver.caltech.edu/CaltechAUTHORS:20160606-082437422

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Abstract

Dissimilatory metal-reducing bacteria can extract free energy from their environment by performing electron transfer to solid-phase minerals outside the cell. This extracellular electron transport (EET) has important implications in global elemental cycles as well as renewable energy technologies. Among the pathways for EET, bacterial nanowires have received significant attention in the past decade due to their unique ability to mediate long-range electron transport to electron acceptors microns away from the cell surface. Here we report a comprehensive characterization of the composition, structure, and regulatory network that underlies bacterial nanowires from the metal-reducing bacterium Shewanella oneidensis MR-1. Using fluorescent and atomic force techniques, we find that the Shewanella nanowires are extensions of the outer membrane and periplasm that contain multiple multiheme cytochromes. The localization of decaheme cytochromes MtrC and OmcA supports a multistep redox hopping mechanism, allowing long-range electron transport along a membrane network of heme cofactors that line the nanowires. The electron flux resulting from such a mechanism strongly depends on the cytochrome density and topology. Using correlated electron cryo-tomography and in vivo fluorescent microscopy, we are gaining new insight into the localization patterns of cytochromes along nanowires as well as the morphology and the formation mechanism of these structures. Finally, we report our progress on understanding the underlying regulatory network, by testing targeted mutations and analyzing the transcriptome of Shewanella chemostat cultures as they encounter electron acceptor limitation and form nanowires. The transcriptional response includes an increase in the expression of multiheme cytochromes, heme synthesis enzymes, and cytochrome maturation proteins. Our findings on the regulation, ultrastructure and electron transport mechanism help shape a biophysical understanding of these redox-functionalized membrane and vesicular extensions as a microbial strategy for electron transport and energy distribution.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.bpj.2015.11.1686DOIArticle
http://www.sciencedirect.com/science/article/pii/S0006349515028696PublisherArticle
ORCID:
AuthorORCID
Jensen, Grant J.0000-0003-1556-4864
Additional Information:© 2016 Biophysical Society. Published by Elsevier Inc.
Record Number:CaltechAUTHORS:20160606-082437422
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160606-082437422
Official Citation:Sahand Pirbadian, Sarah E. Barchinger, Poorna Subramanian, Christine M. Sambles, Carol S. Baker, Nigel J. Burroughs, Grant J. Jensen, John H. Golbeck, Mohamed Y. El-Naggar, Multiheme Cytochromes and the Bacterial Nanowires of Shewanella oneidensis MR-1: Regulation, Structure, and Extracellular Electron Transport Mechanisms, Biophysical Journal, Volume 110, Issue 3, Supplement 1, 16 February 2016, Page 314a, ISSN 0006-3495, http://dx.doi.org/10.1016/j.bpj.2015.11.1686. (http://www.sciencedirect.com/science/article/pii/S0006349515028696)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67675
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:06 Jun 2016 16:35
Last Modified:23 Apr 2019 00:20

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