Systems biology of the gut: the interplay of food, microbiota and host at the mucosal interface.

Our intestinal tract is colonized since birth by complex and subject-specific microbial communities that interact with the host. The human adult microbiota has recently been characterized by deep metagenomic sequencing and several hundreds of intestinal genomes have been characterized at the sequence level. Moreover, the transcriptional response of the host and selected microbes has been identified both in animal model systems and in human. Similarly, the transcriptional response of the host to different diets has been determined in humans, germ-free and gene knockout animals. These developments bring the intestinal tract in the realm of systems biology. An integrated, modular modelling framework that cross-links top-down and bottom-up approaches for the various levels of biological organization is paramount for the understanding of intestinal function.