FIGURE 1.

Changes in gut microbiota composition at different life stages. Microbiota colonization may begin in the uterus as evidenced by the presence of bacteria in the placenta, amniotic cavity, umbilical cord, and meconium. The mode of delivery at birth has a direct effect on the bacterial community. The gut microbiota is initially established at approximately 3 years of age and matures at the onset of adulthood with the establishment of dietary habits, leading to a more diverse and stable gut microbial community. In old age, the gut microbiota is drastically altered and diversity is greatly reduced.