Abstract
The mammalian gastrointestinal tract harbors a highly diverse microbial population termed the microbiome, which plays a major role in nutrition, metabolism, protection against pathogens, and development of the immune system. It is estimated that at least 1000 different bacterial species cohabit the human intestinal tract. Herein we provide a brief review of the developing intestinal microbiome, with the understanding that its development often begins before birth and that disturbance in the microbiome during fetal life, birth, and shortly thereafter may result in adverse consequences. Postnatally, numerous environmental factors including premature delivery, mode of delivery, antibiotic usage, and diet can play an important role in how the intestinal microbiome of infants is shaped. The fact that human milk contains microbes is likely to have important ramifications. We discuss where these microbes come from and their potential role.