Germ-free organisms are multi-cellular organisms that have no microorganisms living in or on them. Such organisms are raised using various methods to control their exposure to viral, bacterial or parasitic agents.[1] When known microbiota are introduced to a germ-free organism, it usually is referred to as a gnotobiotic organism, however technically speaking, germ-free organisms are also gnotobiotic because the status of their microbial community is known.[2] Due to lacking a microbiome, many germ-free organisms exhibit health deficits such as defects in the immune system and difficulties with energy acquisition.[3][4] Typically germ-free organisms are used in the study of a microbiome where careful control of outside contaminants is required.[5]