Giulia Enders

Another trick is to snatch the bad bacteria’s food away (anyone with siblings may be familiar with this strategy).

But sometimes our bacterial community faces attack. That can be from antibiotics, a bad diet, illness, stress, and many, many other causes. Our guts are then less well cared for, less protective, and less good at giving advice.

The fact that almost all the probiotics we know—give or take a yeast or two—are lactic-acid bacteria shows how little we have yet discovered in this area. Lactobacilli are normally less common residents in the guts of adults, and Bifidobacteria are unlikely to be the only health-promoting microbes present in the large intestine.