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Published February 16, 2016 | public
Journal Article

Electron Cryo-Tomography of Nanowires in Shewanella Oneidensis MR-1

Abstract

The dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1 is known to make 'nanowires,' conductive cell appendages used in electron transport. Novel live fluorescence imaging techniques recently clarified that the conductive filaments in S. oneidensis are not pili, as previously thought, but rather extensions of the outer membrane. However, their fine structure and mechanism remained unclear. Here, we report the first high-resolution in vivo images of nanowires in frozen-hydrated cells in a near-native state by electron cryo-tomography (ECT). We first developed a method for in vivo production of nanowires in cells grown on EM grids. Using correlative light microscopy and ECT, we then identified and imaged nanowires at high resolution and in three dimensions. Interestingly, we find that nanowires are composed of outer membrane vesicles (OMVs) strung together to form a chain. The size of the vesicles and the length and thickness of the vesicle chain are highly variable. However, even apparently smooth filaments such as those described previously are in fact, at higher resolution, revealed to be chains of OMVs. This work will help us investigate the electron transport mechanism along Shewanella nanowires. Additionally, this work has implications in understanding how OMVs, ubiquitous in Gram-negative bacteria, can assemble into chains.

Additional Information

© 2016 Biophysical Society. Published by Elsevier Inc.

Additional details

Created:
August 20, 2023
Modified:
October 18, 2023