Adding new bacterial species at high numbers to the gut ecosystem can lead to complex interactions and a new ecology.

“So, the first is that I think it really reinforce this idea that we have this complex ecosystem, like a rain forest, inside of us, and you could imagine that adding a bunch of new species had high numbers to a rainforest doesn't just result in those new species being there, but could lead to an entirely different chain of interactions and ecology that would crop up over a certain period of time. So it's not hard to believe that you would new species flourishing in the presence of this new community members added at high numbers.”