Host Microbiota Contributes to Health and Response to Disease.

Recent studies have revealed that normal microbiota interacts with the host through four mechanisms: the normal microbiome acts as a barrier against pathogens; second, as modulators of the permeability of host mucosa; third, as modulators of energy extraction from, and metabolic utilization of ingested food; and lastly, as modulators of the immune system. An alteration of the normal microbiota increases predisposition of the host to diseases through these four mechanisms.