Question

One of your classmates mentioned on the discussion board that germ-free and gnotobiotic mice can be used interchangeably. Is this true? If yes, explain the methods used to generate each kind of mouse, and if not, explain how they are different. (4 pts)

Answer 1

Germ-free and Gnotobiotic are not the same terms, and therefore can not be used interchangeably. Germ-free mice are mice without any microorganisms associated with the mouse, either in the gut or on any other surfaces of the mouse. However, a Gnotobiotic mouse is a mouse where the microbial species colonizing the mouse are known.

Germ-free mice are produced by in-vitro fertilization of germ-free female mice. If a germ-free female is not available, germ-free mice are generated by in-vitro fertilization of a normal female, and premature cesarian birthing of the progeny. This reduces the chances of contact with any microorganisms and allows a germ-free mouse line to be established, which can then be propagated.

Gnotobiotic mice are mice where the microbial flora colonizing the mouse is known. In a sense Germ-free mice are gnotobiotic in the sense that they are mice with no known bacterial colonists. Gnotobiotic mice are generated from Germ-free mice by introducing the microbial species of interest into the germ-free mice.