In vivo subcellular ultrastructures recognized with Hilbert differential contrast transmission electron microscopy.

We describe the first application of a novel electron microscopic technique to visualize subcellular structures in a near-living state. Rapidly frozen ice-embedded cells provide the most realistic images, as they are free from artefacts induced by sample preparation methods, such as chemical fixation, dehydration, staining and sectioning. The application of the conventional transmission electron microscope to ice-embedded cell imaging, however, has been limited by the low image contrast. The recently developed Hilbert differential contrast transmission electron microscope, which exhibits an unexpectedly high contrast, akin to the differential interference contrast in visible light microscopy, enabled us to clearly discern detailed subcellular structures in ice-embedded cyanobacterial cells.