Developmental microbial ecology of the neonatal gastrointestinal tract

The gastrointestinal tract of a normal fetus is sterile. During the birth p rocess and rapidly thereafter, microbes from the mother and surrounding env ironment colonize the gastrointestinal tract of the infant until a dense, c omplex microbiota develops. The succession of microbes colonizing the intes tinal tract is most marked in early development, during which the feeding m ode shifts from breast-feeding to formula feeding to weaning to the introdu ction of solid food. Dynamic balances exist between the gastrointestinal mi crobiota, host physiology, and diet that directly influence the initial acq uisition, developmental succession, and eventual stability of the gut ecosy stem. In this review, the development of the intestinal microbiota is discu ssed in terms of initial acquisition and subsequent succession of bacteria in human infants. Intrinsic and extrinsic factors influencing succession an d their health significance are discussed. The advantages of modern molecul ar ecology techniques that provide sensitive and specific, culture-independ ent evaluation of the gastroinrestinal ecosystem are introduced and discuss ed briefly. Further advances in our understanding of developmental microbia l ecology in the neonatal gastrointestinal tract are dependent on the appli cation of these modern molecular techniques.