the microbial health factor

The Scientist | Just one molecule can make the difference in mediating a healthy immune response. Surprisingly, it comes from bacteria.

When I trained as a microbiologist around the year 2000, the focus was still on pathogenic bacteria. But I became intrigued by the potential benefits of good bacteria. After all, we’ve coevolved with symbiotic bacteria for millions of years. The hygiene hypothesis, proposed in 1989 by David Strachan1, correlated lower environmental exposure to microbes—as seen in developed countries—with higher rates of allergies. The idea made sense to me. Commensal bacteria help keep pathogenic bacteria at bay, and in the late 1990s new research was beginning to show that symbionts also contribute to the development of the intestinal architecture. If bacteria were so crucial to development, what else might they do? Could they actually make us healthier? Challenging though it was, I was convinced the best way to learn about the systemic effects of bacteria was to start with mice that lacked them entirely.