FIG. 10.

Excerpt from the GroEL (or Hsp60) protein sequence alignment showing a 1-aa insertion (boxed) that is shared by most divisions of G⁻ bacteria but absent from all G⁺ bacteria. The absence of this insert in Thermus aquaticus and Deinococcus proteolyticus, which are diderm prokaryotes that contain thick cell walls, indicates that this insert was introduced into an ancestral gram-negative lineage after the branching of the Deinococcus-Thermus group (thick arrow in the top diagram).