Asymmetric cell-cell adhesion can trigger mitochondriogenesis: A hypothesis

Without exception, modern hypotheses explaining the origin of eukaryotes assume evolution from two (or more) distinct prokaryotes. Almost all prokaryotic cell membranes possess a chemiosmosis system, whereas eukaryotic cell membranes have lost that ability. Nevertheless, no hypothesis describes how chemiosmosis might have been lost from one symbiont. This work proposes a novel hypothesis for the origin of eukaryotes, invoking the adhesion of two chemiosmosis-bearing membranes to promote eukaryogenesis. The intermembrane space between the adhered cell membranes accumulates protons, and the enhanced proton gradient across the membranes accelerates ATP synthesis in both symbionts. Next, the smaller symbiont is engulfed by the larger symbiont to expand the intermembrane space, and then the engulfed symbiont starts to supply a large quantity of ATP to the surrounding host to improve the evolutionary fitness of the whole symbiotic union. Finally, the host cell membrane acquires pluripotent membrane excitation in exchange for its own chemiosmosis system.