From Seed to Seed:
Plant Science for K-8 Educators

Antibiotics and Aspirin

Antibiotics. Gardeners with black walnut trees know that the tree's roots can have an allelopathic effect on nearby vegetation. Allelopathy is the process of one plant producing a chemical that negatively affects a nearby plant or plants. Juglone, a substance in the tree's roots, inhibits the growth of many other types of plants.

Antibiotics offer another example of allelopathy. The effectiveness of antibiotics depends on the fact that the presence of one organism can inhibit the growth of another organism. We want our antibiotics to kill-or at least inhibit the growth of-certain disease-causing microorganisms. Yet they must be harmless to other organisms-namely, us!

As early as 2000 B.C., the Chinese were said to have applied green mold to relieve skin ulcers. In 1877, Pasteur and Jaubert observed that anthrax bacteria were destroyed by other microorganisms. But the real breakthrough came in 1928, when Sir Alexander Fleming noted that a specific green mold, Penicillium, had contaminated the bacteria cultures he had been growing in his lab. The discovery of penicillin was the result of Fleming's astute observation that this "contaminant" was destroying the disease-causing bacteria he was culturing.