1) The gut microbiota plays a key role in host development, physiology, and health by modulating the immune system and influencing organ development and metabolism.
2) The gut microbiota is dominated by anaerobic bacteria and contains over 500-1000 bacterial species from a few bacterial phyla. It outnumbers human cells 10:1 and contains many metabolic functions.
3) The gut microbiota influences the properties of the intestinal mucus layer, induces the development of lymphoid structures, and tailors immune development through effects on both the innate and adaptive immune systems.