Comment by 0cf8612b2e1e

I think author is saying that you ingest compound A, microbe 1 eats A and secretes B, microbe 2 eats B and releases C. C happens to do <positive thing>. You could imagine parallel pathways where maybe microbe 2 only works if it is in the presence of microbe 3.

Meaning everything is a mess to try and disentangle.