It's a humming agricultural community. Leaf-cutter ants forage for plant tissue to feed to their garden of fungus and bacteria, which then provides the ants with food. "The system is not an ant-fungus mutualism in isolation," says Cameron Currie at the University of Wisconsin, Madison. "We've been discovering other microbes within this community." There is also a parasitic fungus that attacks the garden, but bacteria growing on the ants provide antibiotics that treat the fungus — if the yeast that eats the bacteria on the ants is kept in check.
Currie and his colleagues have been studying this system for a decade. During the past two years they have begun to use genomic methods to study the genetic underpinnings of the community's co-evolution and how the system can inform biofuel research. In addition to NSF and DOE grants that focus on sequencing the antibody-producing bacteria and the fungus garden bacteria, respectively, Currie and his colleagues recently received the Roche Applied Science 10G award that will allow them to sequence the ants' genomes as well as more of the bacteria and fungus.
For that award, Currie has prepared and sent DNA from the ants and microbes for Roche to sequence 10 gigabases' worth of data. He expects to have the first set of data from the ants back soon. From that, the researchers will first focus on getting the ant genome together. "Working on an insect genome, especially from a group that has no published genomes, it's a huge project to accurately and fully annotate and validate the stuff and close gaps," Currie says, adding that they will be working on the project with George Weinstock at Washington University in St. Louis. Their long-term goal is even more ambitious: to understand how the intricate web of interactions of the fungus garden system evolved over time.
They also hope to improve biofuel research. Leaf-cutter ants are a dominant herbivore in the Western Hemisphere, Currie says. They, and their fungus garden, process a tremendous volume of plant biomass efficiently — something that biofuel researchers can't do when converting plant biomass to ethanol. "We're studying this natural and very highly evolved bioconversion of plant biomass in the plant system to inform our own attempts to break down part-plant biomass to produce ethanol," Currie says.
The ant fungus garden project will also be part of the microbial sciences department's outreach program. A colony of ants and its fungus garden will be on display for visitors, both in the building and through a live Internet feed. Currie and his colleagues hope to engage high school and college students to learn about the ants, biofuels, evolution, and genomics. Some college students may even help the researchers annotate their new genome sequences, though Currie says plans aren't yet finalized.