The human body is covered with 100 trillion bacterial cells. The normal human microbiome
has a complex symbiotic relationship with the human body and the immune system. Unique
communities of bacteria populate our skin, lungs, genital tract, and intestinal tract, each with
distinct subcommunities defined by the adjoining cells, the availability of nutrients, and the
immune interactions. 1 Although it is recognized that humans are multicellular organisms,
that this multicellularity includes its microbiome and its various interactions with other …