One of the generally agreed-upon criteria for a healthy gut microbiome has been its diversity and the abundance of microbial species present in it. As in the natural ecosystems around us, high diversity of the microbiome means resilience and low diversity means vulnerability to perturbations. Fewer microbial species means a diminished ability to withstand perturbations such as infections (by pathogenic bacteria, viruses, or the pathobionts living in our gut), poor diet, or medications.
