[jp555]

Do we know specific pro-biotic species that have been found to be significantly more beneficial than the rest? How do we know?

Does "pro-biotic" refer only to beneficial prokaryotic organisms or are there known beneficial "pro-biotic" foreign eukaryotes?

[sciencerobot]

Lots of correlations and associations but no Koch's Postulate as far as I know.

[blacksmith_tb]

There are some eukaryotes, yes, e.g. Saccharomyces boulardii.

[jp555]

Ah the yeasts! I recently heard that middle-eastern ancients regularly rubbed old-bread on wounds to speed recovery. Probably more for penicillin mold, but maybe the yeasts were at play as well?