Figure 6

Schematic showing the acquisition and derivation of stator genes through bacterial evolution.

First, the ancestral bacteria acquired the Na⁺-driven stator and earliest branched bacteria have the Na⁺-driven stator. The stator then was converted into the H⁺-driven type through the middle period of bacterial evolution. The Na⁺-driven stator of the late-branched bacteria seems to be provided from early-branched bacteria (Aquificae or Thermotogae) by lateral gene transfer.