Endosymbiosis: Quick Facts

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Facts

Also Known As	endosymbiont

Photos

Diagram of endosymbiotic theory. In primary endosymbiosis, a proto-eukaryote develops a nucleus and endoplasmic reticulum, engulfs aerobic bacteria that become mitochondria, then photosynthetic bacteria that become chloroplasts, forming a modern photosynthetic eukaryote. In secondary endosymbiosis, an ancestral host cell with mitochondria engulfs a photosynthetic eukaryote; its degenerated nucleus remains as a nucleomorph and its chloroplast gains four surrounding membranes.

Color-enhanced electron micrograph showing yellow mitochondria and blue endoplasmic reticulum within magenta-stained hepatocyte liver cells at high magnification.

Riftia pachyptila (giant tube worms) with bright red plumes and long white tubular bodies clustered around a deep-sea hydrothermal vent on the ocean floor.

Close-up of a citrus mealybug (Planococcus citri), a small, soft-bodied insect covered in white, waxy filaments, clinging to a plant stem. The pest appears oval-shaped with fine, thread-like projections along its body, feeding on plant sap and commonly found on leaves, stems, or fruit of tropical and ornamental plants.

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endosymbiont hypothesis symbiosis