New techniques in the rapid freezing of cells, so that they are vitrified, and cryo-transmission electron microscopy (cryoTEM) of the frozen hydrated thin-sections from the vitrified cells are showing their true native structure. Unlike other forms of TEM, frozen hydrated thin-sections cannot be contrasted by heavy-metal stains (such as U, Pb, and Os) and their contrast is via the inherent density of the constituent molecules within the cells. Therefore, these frozen sections show the true mass distribution within the biomatter. Another cryoTEM technique, freeze-substitution, also produces thin sections for viewing by TEM, but these are plastic sections of heavy-metal stained cells. The heavy-metal ions of the stain complex to the available reactive sites of the biomatter. When such images are compared to those from the frozen hydrated sections, a clear interpretation of native structure and its metal reactivity can be made. These types of observations will be invaluable for the study of microbe-metal/radionuclide interactions.
The Japan Society of Nuclear and Radiochemical Sciences