The host microbiome has been firmly established as critical to host physiology. However, many members of this community have yet to be cultured and characterized. As such, it remains difficult to ascribe their contributions to gut and systemic function, and thereby, host health and well-being. In this talk I will be discussing the use of population genomes recovered via metagenomic sequencing to fill in these knowledge gaps using as illustration an example of an abundant but uncultured family present within the mouse gut microbiota.