Endosymbiosis and sulfur bacteria (1967)
Lynn Margulis (then Sagan) published the endosymbiotic theory, proposing that mitochondria descend from bacteria engulfed by early cells. Sulfur-respiring bacteria store elemental sulfur in granules.
The theory was initially rejected, then became a cornerstone of cell biology.
It reframed mitochondria as bacterial descendants carrying their own biochemistry.
Finding S8, a molecule bacteria store, inside mitochondria suggests a biochemical legacy from those sulfur-metabolizing ancestors.
