Germ-free animal

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Germ-free animals are animals that have no microorganisms living in or on them. Such animals are raised within germ-free isolators in order to control their exposure to viral, bacterial or parasitic agents.[1] When known strains of bacteria or microbiota are introduced to a germ-free animal, it usually is referred to as a gnotobiotic animal, however technically speaking, germ-free animals are also gnotobiotic because the status of their microbial community is known.[2]

Germ-free animals are used in the study of probiotic research and other animal research requiring careful control of outside contaminants that can affect the experiment.[3] They also exhibit defects in the immune system.[4] Because intestinal microorganisms provide additional energy to the animal by breaking down dietary fiber, germ-free animals require more food to keep the same weight than animals that are not germ-free.[citation needed]

See also[edit]


  1. ^ University of Michigan Germ Free Animal Facility - example facility for raising germ-free animals
  2. ^ Reyniers, J.A. (1959). "Germfree Vertebrates: Present Status". Annals of the New York Academy of Sciences. 78 (1): 3. doi:10.1111/j.1749-6632.1959.tb53091.x.
  3. ^ Of Probiotics and Possibilities - J. Armbrecht. Dept of Bacteriology, University of Wisconsin-Madison. August 2, 2000.
  4. ^ Round, JL; Mazmanian, SK (May 2009). "The gut microbiota shapes intestinal immune responses during health and disease". Nature Reviews. Immunology. 9 (5): 313–23. doi:10.1038/nri2515. PMC 4095778. PMID 19343057.