Courtesy of Frederic D. Bushman
The endosymbiotic theory, which posits that organelles such as chloroplasts and mitochondria descended from formerly independent cells, has received wide acceptance in the last third of the 20th century. But recent findings suggest that endosymbiotic processes may have contributed still more cellular components, chloroplasts and mitochondria being simply the most easily identified examples.
Genomic analyses across a broad spectrum of organisms have solidified the case for mitochondria and chloroplasts and suggested that less well known organelles, the hydrogenosome and mitosome, are remnants of genome-depleted mitochondrial descendants. These findings raise questions as to whether still other structures in eukaryotic cells, now lacking their own DNA, might also have originated through endosymbiosis.
According to the presently favored views on endosymbiosis, an anaerobic cell engulfed a respiring α-proteobacterium, allowing respiration in the resulting consortium. This may have taken place during early evolution concomitant with Earth's planetary transition from ...
