title: Endosymbionts and mitochondrial origins.
abstract: The possibility is put forth that the mitochondrion did not originate from an endosymbiosis, 1-2 billion years ago, involving an aerobic bacterium. Rather, it arose by endosymbiosis in a much early, anaerobic period, and was initially a photosynthetic organelle, analogous to the modern chloroplast. This suggestion arises from a reconsideration of the nature of endosymbiosis. It explains the remarkable diversity in mitochondrial information storage and processing systems.
mesh_terms: D005075:Biological Evolution; D002736:Chloroplasts; D004272:DNA, Mitochondrial / Q000235:genetics; D005796:Genes; D008928:Mitochondria; D010101:Oxygen Consumption; D013559:Symbiosis
chemical_list: D004272:DNA, Mitochondrial