Yes, I have been cultured (erm…sorry) on the joy that is Lactobacillus Acidophilus et al. Instead of spending ~$7/bottle/biweekly, would it be possible to, say, simply replenish what I take from the bottle with some skim milk, and have the little buggers reproduce to full strength again?
It’s a little more complicated than that, but you’ve got the basic idea.
What you are actually trying to do is make your own yogurt. There are plenty of recipes out there, but a simple to follow one is here.