We have been missing a large number of the microbes that live in our body, and we have no idea how they affect our health.

In recent years, we have come to understand that our microbiomes – the microbes that live in our guts and elsewhere – may affect everything from armpit smell to obesity . This realisation has prompted groups around the world to begin developing therapies that target our microbiomes in an effort to treat a range of conditions.

But it appears …