Figure 1
Schematic drawings to indicate the advantage of spherical beads as an alternative of conventional flat substrate for quick-freeze deep-etch replica electron microscopy. (a) Bacterial cells placed on flat surface give only the top- or slightly oblique-views by electron goniometry. (b) Though smoothed ground-glass did not successfully work for quick-freeze replica, it might be still useful as a substrate for the other surface observation apparatuses. (c) Spherical substrate provides the possibility of much wider view-angles including side-, oblique- and frontal-views of the targets. (d) Enlarged views of (a), left; and (c) right, respectively, with the direction to be observed in transmission electron-microscope. (e,f) Elongated bacteria attached along the spherical substrate also give various observation-angles (see the text for details). Attachment of those cells on the convex surface might forcefully extend the outer-side of the curved cell to facilitate weakening and regional opening of the cell wall. In the same way, bacteria cells that bridge two adjacent beads might receive substantial pressure at the elbow, partially exposing the internal structures. Pink-colored segments indicate the portions of internal structure revealed by imposed tension or the pressure as above. (g,h) Are the cartoons exhibiting two extreme cases for clarity, of rotary-shadowing (elevation-angle, 15°) to the targets along the inner-side of the bacterial membrane, where disrupted bacterial bodies (center) are strongly adsorbed to concave (g) and convex (h) substrates, respectively. In (g), protrusions along the inner membrane surface are either partly shadowed (light orange area) or not shadowed at all (black area), whereas all of the protrusions are evenly and fully-shadowed (orange area) in (h). Orange-colored-arrows indicate the direction of rotary-shadowing. Evenly metal-accumulated area increases, if the elevation-angle is changed during the procedure.
