Endosymbiont

Definition

An organism that lives inside another organism, often benefiting both parties. In biology, this term often refers to how certain organelles were once free-living bacteria that got incorporated into early eukaryotic cells.

Related terms

Symbiosis:

A close and long-term biological interaction between two different biological organisms.

Mitochondrial DNA:

The small amount of DNA that is located in the mitochondria of cells, inherited only from the mother, suggesting its origin from an endosymbiotic event.

Chloroplasts:

Organelles found in plant cells and eukaryotic algae that conduct photosynthesis; they are also thought to have originated as endosymbiotic cyanobacteria.