It doesn't end there. This theory may also explain a number of other organelles like flagella, cilia, peroxisomes, centrioles, etc.
Really put into imaginary motion what that means.
You aren't one thing.
You're a host of organisms working together.
You aren't a human.
You're a collective of bacteria.
It gets worse.
If you were to count out all the cells in your body you'd get about 10 trillion or so (I've seen varying estimations of this and the next number). If you were to count out all the bacteria cells in your gut, on your skin and every where else you'd get...drum roll...about 100 trillion.
Let me spell out what that means.
Let me say it another way.
You're about 90% bacteria.
I hope that messes with your head some. It has mine. :)