What is this community of microbes collectively called?

This community of microbes is called the gut microbiome, the trillions of bacteria and other organisms living throughout our intestines that help break down food, train and regulate the immune system, and, according to a growing body of research, may even influence mood and mental health through signals sent to the brain.

The lymphatic system is a network of vessels and nodes that helps circulate immune cells and drain fluid throughout the body, a distinct anatomical system rather than a community of bacteria. The endocrine system refers to the glands that produce hormones, also a separate biological system from the gut's microbial population.

Interest in the gut microbiome has fueled a huge boom in probiotic supplements and fermented foods, though scientists caution that the science connecting specific bacteria to specific health outcomes is still evolving and far less settled than much of the marketing around it suggests.