Right now, "superbugs" resistant to antibiotics are on the rise. These bugs are in part the result of doctors and patients relying too much on just a handful of antibiotics. So researchers are searching for new drugs in unusual places, including fungal gardens cultivated by leaf-cutter ants, writes Alexander Sehmer for How We Get To Next.
Leafcutter ants don’t actually eat the leaves they carefully snip from plants and carry back to their nests. They grow fungus on them. The fungus, mainly from the family Lepiotaceae, digests the leaf pulp conveniently chewed for it by ants. In turn, the insects harvest the fungi for food.
When scientists first studied these ant colonies, they noted they were remarkably pathogen free. At first, scientists thought the cleanliness was due to the ants’ fastidious ways, but then they realized that the ants also kept certain bacteria growing on the fungus. In some colonies, bacteria belonging to the genus Pseudonocardia completely cover the ants that work in the fungus gardens, given them the appearance of being dusted with white powder. Pseudonocardia also produces its own antibiotics, which the ants harness to fight against invading pathogens and molds. If an ant discovers some kind of unknown pathogen, it takes it to a "compost heap," to sterilize it, Sehmer writes.
"The ants have effectively selected new strains of bacteria that we haven’t seen before, and they are making new antibiotics that we haven’t seen before," microbiologist Matt Hutchings, of the University of East Anglia, tells Sehmer.
Hutchings keeps several colonies in his lab. His team collects some of these unique bacterial strains and sequences them to see if they produce any antibodies that could be useful for humans. So far they have collected more than 500 strains.
Finding a new antibiotic takes years, however, because it must pass a series of clinical trials to ensure its safety. But if someday a new antibiotic comes out of this work, it won’t really be that unusual. After all, most of the antibiotics humans use today originally came from soil bacteria. In this case, the ants are just doing some of the groundwork for researchers.