Mitochondria: Where Are They Coming From?

This chapter summarizes the evidence sustaining the concept that mitochondria derive from a particular type of bacteria, the alpha proteobacteria. Once considered a hypothesis, this concept is now a scientific fact and therefore should not be viewed in dubitative terms. What remains uncertain is from which bacterial taxa the proto-mitochondria originated. However, the quest to find the living bacterial relatives of our mitochondria is narrowing to a limited set of alpha proteobacteria with ample metabolic versatility. The results of this quest are likely to throw new light on various aspects of mitochondrial physiology and biochemistry.