@SoldierCrab We may be able to thank koalas and the animal kingdom for letting us know about fecal transfers and gut bacteria. I did wildlife care for a lot of years, and my mentor looked after tiny koalas and taught me that at a certain stage they are given poo from a healthy koala to get their guts right to help them digest eucalyptus leaves. The baby koalas eat it naturally from their Mum in the wild. In captivity when my friend brought out a jar of specially harvested koala poop (not the technical name) the koala joey actually jumped off its little branch and ran across her to get to the jar and eat some! She wasn't game to leave an open jar in the same room as them!