This was a fascinating read, thank you for sharing. Were there really no lasting effects? I'm curious why the introduced bacteria didn't flourish and permanently change your microbiome. Can anybody weigh in?
It might be that they have to hit a certain critical mass to become self-sustaining. Or they require a particular environment to thrive, which exists in the donor but not in the donee. It's such a new field, at least for prescriptive medicine, that it'll probably be a while before we get a good base of understand of what lives in our gut, what it does, and how to keep it healthy.
My money is indeed on the environment. You'd want to know what that donor was eating, and try to replicate it.
We are what we eat. Could try changing to the same diet as the donor...