For transmission electron microscopy (TEM) analyses of M. gryphiswaldense cells and isolated magnetosomes, specimens were deposited onto carbon-coated copper-mesh grids (Science Services, Munich, Germany). Isolated particles were additionally negatively stained with 2% uranyl acetate. TEM was performed on a JEOL 1400 (JEOL, Tokyo, Japan) with an acceleration voltage of 80 kV. Images were taken with a Gatan Erlangshen ES500W CCD camera.
For localization studies, neurons, both control and stretched, were fixed with 1.5% glutaraldehyde in 0.1 M sodium cacodylate buffer, at pH 7.4. After rinses with the same buffer, cells were post-fixed in reduced osmium tetroxide solution (1% OsO4, 1% K3Fe(CN)6, and 0.1 M sodium cacodylate buffer), stained with our homemade staining solution [52 (link)], dehydrated in a growing series of ethanol, and flat-embedded in epoxy resin.
Ultra-thin sections (90 nm) were cut with a UC7 LEICA ultramicrotome (UC7—Leica Microsystems, Vienna, Austria) and collected on 300 mesh copper grids (EMS—Electron Microscope Science, Hatfield, PA, USA).
Images for morphological characterization have been collected with a Transmission electron microscope Zeiss LIBRA 120 Plus operating at 120 KeV equipped with an in-column omega filter.
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