Just say "gnotobiotic."

One from the obscure word file today: gnotobiotic. That’s “nəʊtəʊbaɪˈɒtɪk” in IPA notation, which by my crude phonetics is roughly “no-toe-bi-ah-tic.”

If you work in research in the life sciences you might know this word. You might even work with gnotobiotic animals, although it’s not common: gnotobiotic animals are difficult to produce, and they require special conditions.

Gnotobiotic animals are those animals raised with no bacteria in their environment. They’re “germ-free,” which makes them valuable for certain types of research. For example, a researcher might want to see how the immune system of a typical mouse develops, as opposed to that of a mouse raised with no naturally occurring bacteria in its gut. Using gnotobiotic mice would make it possible to conduct this experiment.

This sort of work has revealed important information about the role symbiotic bacteria play in other organisms. Gnotobiotic animals are used in research involving autoimmune disorders, drug metabolism, genetic expression, and numerous other fields.

Gnotobiotic is a relatively new word, and it doesn’t see frequent use. OED points to first use in a 1949 article appearing in the LOBUND Report, a long-since retired publication of the LOBUND Institute. “LOBUND,” as far as I can tell (the online sources are a bit sketchy), was the “Laboratory of Bacteriology at the University of Notre Dame,” which began around 1928, existed as an independent entity beginning some time in the 1940s, and was reabsorbed into Notre Dame’s biology department in 1958. In 1957, the launch of the first Ph.D. program in gnotobiotics was noted in Science News. It’s never been a huge field, but there are still several dedicated gnotobiotic facilities in the US. Judging by a cursory comparison using Google, the word is still primarily used by specialists, and the specialist pool isn’t vast: “gnotobiotic” appears in publicly visible documents only about 1.2% as often as “apoptosis,” another specialized (but much more widely used) life sciences term. (That’s a very unscientific comparison, the way I randomly used apoptosis and Google, and I know it, but it’s better than nothing.)

I need to note here that some might take issue with the definition of gnotobiotic that I gave above. “Germ free” or “bacteriologically sterile” or “devoid of all other organisms” is the standard book definition of gnotobiotic. However, gnotobiotic researchers working in the field might note that the word really means “known bacteria.” It is, in fact, a compound derived from the Greek “gnoto” (“known“) and “bios” (“life“). The original intent was for the word to signify not that an animal was raised in an entirely sterile, germ-free environment, but rather that it had been created in a sterile environment and was then raised in a controlled environment with only a very limited number of the hundreds, or thousands, of different types of bacteria that would normally colonize that host organism. To some, especially outside the field, the difference in the definitions might seem too small to worry over, but to others its very important.

Exactly how much effort is involved in creating gnotobiotic animals? Take a look at this 2004 PNAS paper by Rawls, Samuel, and Gordon involving gnotobiotic zebrafish. The procedure used to raise them is described under “Germ-free (GF) zebra fish” in the Materials and Methods section. While many readers will not like seeing the details of what has been done to zebrafish in the name of science and health research, well-designed gnotobiotic experiments like these continue to contribute to our understanding of life in all its forms.

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