ABSTRACT
The microbiota of the human gastrointestinal tract and in particular the large intestine,
comprises a large and diverse range of microorganisms, with over 1012 bacteria per gram
of contents (1). It is therefore not surprising that the activities of this microbial population
have a significant impact on the health of the host. The microbiota interacts with its host at
both the local (intestinal mucosa) level, and systemically, resulting in a broad range of
immunological, physiological, and metabolic effects. From the standpoint of the host,
these effects have both beneficial and detrimental outcomes for nutrition, infections,
xenobiotic metabolism, toxicity of ingested chemicals, and cancer.
