Gut biogeography of the bacterial microbiota

The gut microbiota has a strong impact on host physiology. In this Review, Mazmanian and colleagues describe the mechanisms that control the biogeography of bacteria in the gut and discuss the importance of the spatial localization of the gut microbiota during health and disease. Animals assemble and maintain a diverse but host-specific gut microbial community. In addition to characteristic microbial compositions along the longitudinal axis of the intestines, discrete bacterial communities form in microhabitats, such as the gut lumen, colonic mucus layers and colonic crypts. In this Review, we examine how the spatial distribution of symbiotic bacteria among physical niches in the gut affects the development and maintenance of a resilient microbial ecosystem. We consider novel hypotheses for how nutrient selection, immune activation and other mechanisms control the biogeography of bacteria in the gut, and we discuss the relevance of this spatial heterogeneity to health and disease.