EM images of an internal core.

The core can be divided into three parts: a terminal button, paired plates, and a bowl (wheel) complex. Yellow arrows indicate the boundaries between parts. Bold (A), slim (B), fork (C), and branched (D) types are aligned as the cell front on the right. A less-dense area in (C) is marked by an asterisk. (E-G) Structural features of bowl complex. Two typical images are magnified for the bowl (E), the paired plates (F), and the terminal button (G). Yellow arrowheads indicate the boundaries between parts. The original and colored images are shown in the adjacent panels in (E) and (G). Bold and slim structures are shown in the upper and lower panels, respectively. (E) The bowl complex can be divided into two parts, an arch (dark yellow) and accessories (light yellow). (F) The plate in the slim type has a bend around 60 nm from the back end, as marked by the yellow triangle. (G) The terminal button can be divided into a small oval (dark yellow) and accessories (light yellow). (H) Schematics and dimensions of bold (left) and slim (right) types of internal core images. Each length shown is the average of 40 structures.