Fig. 1
From: Breath-giving cooperation: critical review of origin of mitochondria hypotheses
Scenarios of the various mitochondrial origin models. Scenarios focus mostly on topological changes, after the works of Martin and others [12, 31, 57, 68, 109]. Archaea are depicted with red membrane, Bacteria with blue; purple indicates photosynthetic ability. Dashed curves stand for degrading membranes. If not indicated syntrophic “engulfment”, the inclusion involved phagocytosis (even if primitive) with at least a rudimentary cytoskeleton (indicated by the host forming phagosomal inclusions). If not indicated otherwise, mitochondria perform aerobic respiration. Ultimately, in all scenarios, mitochondria implement metabolic compartmentation and produce ATP. 1) Hydrogen hypothesis [12, 45, 67]. 2) Photosynthetic symbiont theory [36, 37, 74]. 3) Syntrophy hypothesis [48, 110]. 4) Phagocytosing archaeon theory [16]. 5) Pre-endosymbiont hypothesis [9, 41]. The origin of the endomembrane system (and nucleus) is not specified explicitly, but one must assume that it evolved endogenously, the pre-endosymbiont (brown organelle) being related to the internal membrane system. 6) Sulfur-cycling hypothesis [46, 57, 111]. 7) Origin-by-infection hypothesis [57]. 8) Oxygen-detoxification hypothesis [68, 69, 103]. The presence of a forming nucleus at the start is unknown [68]