Identification of Population Bottlenecks and Colonization Factors during Assembly of Bacterial Communities within the Zebrafish Intestine.

Zebrafish larvae, which are amenable to large-scale gnotobiotic studies, comprehensive sampling of their intestinal microbiota, and live imaging, are an excellent model for investigations of vertebrate intestinal colonization dynamics. We sought to develop a mutagenesis and tagging system in order to understand bacterial population dynamics and functional requirements during colonization of the larval zebrafish intestine. We explored changes in bacterial colonization dynamics and functional requirements when bacteria colonize a bacterium-free intestine, one previously colonized by their own species, or one colonized previously or simultaneously with a different species. This work provides a framework for rapid identification of colonization factors important under different colonization conditions. Furthermore, we demonstrate that when colonizing bacterial populations are very small, this approach is not accurate because random sampling of the input pool is sufficient to explain the distribution of inserts recovered from bacteria that colonized the intestines.