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Correlative Electron and Fluorescence Microscopy of Magnetotactic Bacteria in Liquid: Toward In Vivo Imaging

TitleCorrelative Electron and Fluorescence Microscopy of Magnetotactic Bacteria in Liquid: Toward In Vivo Imaging
Publication TypeJournal Article
Year of Publication2014
AuthorsWoehl, TJ, Kashyap, S, Firlar, E, Perez-Gonzalez, T, Faivre, D, Trubitsyn, D, Bazylinski, DA, Prozorov, T
JournalScientific Reports
Date Published10
Type of ArticleArticle
ISBN Number2045-2322
Accession NumberWOS:000343989600005
Keywordscells, gold nanoparticle uptake, growth, magnetite formation, magnetosome formation, nanocrystals, nanomaterials, nucleation, situ, viability

Magnetotactic bacteria biomineralize ordered chains of uniform, membrane-bound magnetite or greigite nanocrystals that exhibit nearly perfect crystal structures and species-specific morphologies. Transmission electron microscopy (TEM) is a critical technique for providing information regarding the organization of cellular and magnetite structures in these microorganisms. However, conventional TEM can only be used to image air-dried or vitrified bacteria removed from their natural environment. Here we present a correlative scanning TEM (STEM) and fluorescence microscopy technique for imaging viable cells of Magnetospirillum magneticum strain AMB-1 in liquid using an in situ fluid cell TEM holder. Fluorescently labeled cells were immobilized on microchip window surfaces and visualized in a fluid cell with STEM, followed by correlative fluorescence imaging to verify their membrane integrity. Notably, the post-STEM fluorescence imaging indicated that the bacterial cell wall membrane did not sustain radiation damage during STEM imaging at low electron dose conditions. Weinvestigated the effects of radiation damage and sample preparation on the bacteria viability and found that approximately 50% of the bacterial membranes remained intact after an hour in the fluid cell, decreasing to similar to 30% after two hours. These results represent a first step toward in vivo studies of magnetite biomineralization in magnetotactic bacteria.

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Protein Templated Nanocrystals