Researchers from around the world have teamed up to detail the ancient history of ant and fungus co-evolution, providing new contexts for antimicrobial drug discovery.

A diverse collection of ant species have symbiotic relationships with fungi, which they farm, protect and harvest for food. These fungi have evolved in tandem with ants for millions of years, according to the study, published this month in the journal Science.

While the relationship has been well studied in recent years, the origins of ant-fungi agriculture have remained poorly understood — until now.

Researchers studied thousands of genetic samples in the largest study of its kind to develop a detailed evolutionary tree for hundreds of different ant and fungi species, tracking their evolution together over time.

The new data reveals that fungus-ant agriculture began around 66 million years ago, after an asteroid collided with Earth. The impact caused debris to spew up into the atmosphere, which blocked out the sun. This interrupted photosynthesis and caused mass extinctions, but fungi, which don’t photosynthesize, thrived.

Researchers at the Smithsonian Institution led the international collaboration, which includes critical contributions from McMaster scientist Cameron Currie, a professor in the department of Biochemistry and Biomedical Sciences.

“Being able to grow your own food is a major innovation,” Currie says. “For humans, doing so was critically important for increasing our population density, and it enabled a release of labour that really let us focus on developing other areas of our society.”

The new paper was decades in the making, involving both painstaking field work and detailed lab science, Currie says.

Many of the study’s collaborators contributed ant and fungi samples derived from live colonies excavated from a range of sites in the tropics.

“With the ants themselves, you can collect foragers that are wandering around outside of the colony and preserve them for DNA sequencing,” he says.

“But to get the fungal cultivar, you need to carefully excavate the colony and successfully stabilize it and maintain it in the lab so that it can be cultured and grown for DNA extraction and sequencing.”

The study provides critical new context for his own research program, says Currie, the Jarislowsky Chair in Pandemic Research and Prevention and a member of the Michael G. DeGroote Institute for Infectious Disease Research.

His lab is focused on harnessing another ant symbiont — antibiotic-producing bacteria that ants leverage to keep their fungal gardens free from disease — as a source of novel antimicrobial medicines.

“This study further establishes ant-fungi agriculture as an ancient system,” he says.

“The fact that it has remained really stable and successful in the face of disease threats for millions of years validates the potential of these ants as a source of new drugs, and as an interesting case study for both biomedical science and human agriculture.”