A human being consists of a mammalian component and a multiplicity of microbes, collectively referred to as the "microbiota" or "microbiome," with which it has a symbiotic relationship. The microbiota is comprised of a variety of communities, the composition of each being dependent on the body site it inhabits. This community variation arises because the numerous locations on a human being provide very different environments, each of which favors the establishment of a distinct microbial community. Each community consists of bacteria, fungi and viruses with, in some cases, archaea and/or...