Poo transplants and probiotics

For more than one hundred years, we believed avoiding bugs or removing them from our system was the simplest way to improve our health.

But while tremendous public health advances have come from controlling dangerous pathogens, we now understand the trillions of other bacteria that live in our body – and in particular, our gut – perform a range of important functions.

So when, and how, should we try to manipulate these microorganisms, collectively referred to as our microbiome?