Most medically important antibiotics come from soil bacteria. Conventional wisdom holds that dirt microbes evolved these compounds as lethal weapons in the fierce battle waged beneath our feet for food and territory. For more than 15 years microbiologist Julian Davies of the University of British Columbia has been arguing otherwise. “They’re talking, not fighting,” Davies says.
His respected if not wholly accepted theory is that bacteria use most of the small molecules we call antibiotics for communication. As evidence, Davies points out that in nature, soil bacteria secrete antibiotics at trace levels that do not come close to killing their microbial neighbors. “Only when we use them at unnaturally high concentrations do we find that these chemicals inhibit bacteria,” he explains.