Intestinal colonization: how key microbial players become established in this dynamic process: microbial metabolic activities and the interplay between the host and microbes.

In this review, we provide an overview of the dynamic changes within the microbiota and its metabolites that are implicated in establishing and maintaining gastrointestinal homeostasis during various stages of microbial colonization. The gradual conversion of the gut microbiota toward a mutualistic microbial community involves replacement of pioneer gut colonizers with bacterial taxa that are characteristic for the adult gut. An important microbial signature of homeostasis in the adult gut is the prevalence and activity of a diverse spectrum of bacterial species that produce beneficial metabolites through metabolic interactions between microbial groups. Deciphering these microbial signatures and their metabolites that govern short and long-term equilibrium, as well as imbalances in host-microbial relationships, may provide novel diagnostic tools and/or therapeutic targets for specific disorders associated with intestinal dysbiosis and loss of homeostasis.