Gnotobiotics, << `noh` toh by OT ihks, >> is the scientific study of animals or other organisms raised in environments that are free of germs or that contain only specifically known germs. Scientists compare gnotobiotic animals with ordinary animals whose bodies carry many bacteria, viruses, and parasites. In this way, scientists can determine more precisely how specific germs affect the body. Gnotobiotics has aided the study of metabolism and other body functions, of the interaction of various germs in the body, of organ and tissue transplantation, and of the effects of radiation on the body.
Gnotobiotic animals are obtained by removing unborn animals from their mother’s womb and putting them into a sterilized cage called an isolator. Rats and mice are two types of animals frequently used. Rubber gloves built into the isolator enable scientists to handle and care for the animals without contaminating them. All food, water, and other supplies are sterilized before being put into the isolator.
Gnotobiotic animals look like ordinary animals and are fully capable of normal life functions, such as survival, growth, and reproduction. However, they differ from ordinary animals in some ways. The major differences in gnotobiotic animals are in the size of organs that come in direct contact with germs, such as organs of the digestive tract and respiratory system. For example, the small intestine of gnotobiotic animals is generally shorter and thinner and the cecum (part of the large intestine) generally much larger than those of ordinary animals. Gnotobiotic animals also have lower rates of metabolism, heartbeat, and blood flow than do ordinary animals. In addition, gnotobiotic animals are less resistant to disease.
