The endosymbiotic theory holds that organelles within the cells of eukorytes such as mitochondria and chloroplasts, had descended from independent bacteria that came to live symbiotically within other cells.
She developed a theory of the origin of eukaryotic organelles, and contributed to the endosymbiotic theory, which is now generally accepted for how certain organelles were formed.
These modern organisms with endosymbiotic relationships with aerobic bacteria have verified the endosymbiotic theory, which explains the origin of mitochondria and chloroplasts from bacteria.
On the other end of the scale, genetic studies support the endosymbiotic theory according to which mitochondria and related organelles developed from members of this group.