The Human Intestinal Microbiota and Microbiome

The microbiota has a major impact on health through interactions with host cells (including components of the innate and adaptive immune systems), through extraction of nutrients and energy from the diet, and through complex biotransformations (e.g., detoxification) of a variety of ingested compounds, including potential carcinogens. To date, two major projects have characterized the healthy human gut microbiota on a large scale: the Metagenomics for the Human Intestinal Tract (MetaHIT) consortium (primarily European and Chinese partners) and the Human Microbiome Project (HMP) consortium. Many diseases associated with an altered gut microbiota are also related to host genetic factors, which have been shown independently to alter the microbiota. One of the best examples of this is Crohn's disease. Variants in genes associated with the adaptive immune system have also been implicated in human disease, and these may play a role in shaping the microbiome.