Ant-Fungus Relationship May Provide New Clues About Antibiotics

The 50-million-year-old relationship between fungus-growing, or attine, ants and the fungus they cultivate and eat has long been considered a model of symbiosis. But researchers at the University of Toronto have found that another factor-- Streptomyces bacteria-- maintains this mutualism. Carried on the ants' bodies, the bacterium produces an antibiotic that specifically targets the virulent parasite that invades the fungal gardens, thereby protecting the fungus that sustains the ants.

"Since the complexity of this well-studied symbiotic relationship was greatly underestimated this suggests that antibiotic-producing bacteria may also be key components in symbiotic associations of other organisms," said principal investigator Cameron Currie, a graduate student in the department of botany.

Currie and his team studied 22 species of attine ants in Panama in 1997 and 1998, all of which had the bacterium. "The type of bacteria found on the ants are a well-known source for human antibiotics," he said, "so further study of these chemical interactions may provide valuable new knowledge about the discovery and application of antibiotics." Currie's co-investigators were graduate student James Scott and Professor David Malloch of botany and Dr. Richard Summerbell of U of T's department of laboratory medicine and pathobiology and the Ontario Ministry of Health. While in Panama Currie worked at the Smithsonian Tropical Research Institute. Funding was provided by the Natural Sciences and Engineering Research Council of Canada and the Smithsonian Institution in Washington.