Hundreds of trillions of bacteria consisting of ~1,000 species reside in various human body sites to form bacterial communities(microbiomes)specific for the sites. In the past decade, the human microbiome research in the world incredibly advanced by development of a culture-independent metagenomic analysis based on next-generation sequencing technologies. Particularly, current studies have revealed that the human gut microbiome is profoundly associated with the host's health and disease.