抄録
Recent studies show that early-life gut microbiota are intimately associated with human health not only during infancy but also in later life. Immediately after birth, the neonatal gut is colonized by members of facultative anaerobic bacteria belonging to the Enterobacteriaceae family and Streptococcus and Staphylococcus genera. However, these bacteria are replaced with obligate anaerobic microbes such as bifidobacteria within a few weeks as the oxygen concentration of the intestinal lumen decreases. Breastfeeding markedly contributes to the formation of bifidobacteria-rich (up to 90 % of total bacteria) "healthy" gut microbiota. In this chapter, we describe how breastmilk mediates the interplay between gut microbes, especially bifidobacteria, and humans infants at the molecular level. Non-digestible oligosaccharides contained in human breastmilk (human milk oligosaccharides; HMOs), which are the third most abundant solid component and comprise over 100 molecules, promote the growth of several Bifidobacterium species (infant-type bifidobacteria) that possess varied enzymatic sets for HMO utilization. The infant-type bifidobacteria that proliferate in the gut in turn convert aromatic amino acids (breastmilk components) to aromatic lactic acids which have physiological relevance to the host e.g. immune system regulation and energy homeostasis. These findings provide the molecular basis underlying symbiosis and co-evolution between infant-type bifidobacteria and humans mediated by breastmilk components.
