Influence of the human gut microbiome on the metabolic phenotype

The gastrointestinal tract supports a vast community of microbes (bacteria, archea, lower eukaryotes, viruses), collectively termed the gut microbiota. Genetic diversity within this microbial ecosystem is some 50-100 times greater than that of the human host. The collective genes of these microbes encode extensive biotransformation capabilities that extend the functional capacity of the host. As such, gut microbes play a significant role in the metabolism of many endogenous, xenobiotic, and dietary molecules and are considered a major component of mammalian biocomplexity. The gut microbiota is highly host specific and shaped by a myriad of intrinsic and extrinsic host factors. Such variation in the compositional structure of the microbiota and its resultant functional variation can influence the metabolic phenotype of the host. This chapter will introduce the key metabolic reactions performed by the gut microbiota and their implications for the host.