And shockingly, it worked! The engineered bacteria replaced the natural mitochondria in the yeast. Wild.
But I guess to answer your question more directly, the cells that don't have the mitochondria would more likely die, because they don't have the fitness advantage.
Eukaryotic cells have multiple copies of their mitochondria, not one. When the cell divides, the mitochondria (roughly) split between the two daughter cells then carry on
For me, the intuitive part is how mitochondria can be created by the body if it's an external structure that's been found. If I take a coin and put it in my pocket, my children don't have any coins at birth. They have to find one themselves. Why is it different for mitochondria?
But to continue the analogy, it's more like you split yourself into two smaller "you"s, and in the process each new "you" gets half a coin in the pocket of each new "you".
An interesting thing about mitochondria too— we receive all of our mitochondria from our mother. So for every human, there is an unbroken line of direct mitochondrial ancestors leading all the way back to the first biologically unique Homo Sapian women
The piece I was missing is that even for large organisms, new life is created by cells (eggs) already containing mitochondria dividing. New cells aren't created from scratch.
: Mitochondrial replication is controlled by nuclear genes and is specifically suited to make as many mitochondria as that particular cell needs at the time.
: Each human cell contains approximately 100 mitochondria
: The amount of mitochondria per cell also varies by cell type
: Egg cell: Mature metaphase II egg cells can contain 100,000 mitochondria
(so when it comes to passing down mitochondria to descendants, eukaryotes don't fool around)
It would be even more miraculous if the cell managed to relate interlopers to just one side for the event. Although you're kind of getting away from cell fission at that point: that's more like birth.
Goodreads: https://www.goodreads.com/book/show/39001.Power_Sex_Suicide