New Microbes Found that Help Leaf Cutter Ants Breakdown Biomass

The Science

Tropical leaf cutter ants cultivate specific fungi to efficiently break down cellulosic plant biomass to serve as food for ant colonies. However, plant materials harvested by the ants contain relatively small amounts of nitrogen, a crucial nutrient that limits the growth of the ants’ fungal gardens and thus breakdown of plant biomass. By using acetylene reduction and stable isotope experiments, researchers demonstrated that N2 fixation occurred in the fungus gardens of eight leaf-cutter ant species and, further, that this fixed nitrogen was incorporated into ant biomass. Symbiotic N2-fixing bacteria were consistently isolated from the fungus gardens of 80 leaf-cutter ant colonies collected in Argentina, Costa Rica, and Panama. The discovery of N2 fixation within the leaf-cutter ant−microbe symbiosis reveals a previously unrecognized nitrogen source in neotropical ecosystems.


In a paper in the November 20 issue of Science, researchers at the DOE Great Lakes Bioenergy Research Center (GLBRC) describe how bacteria colonizing the ant gardens convert atmospheric nitrogen gas into ammonia, a form of nitrogen that can be used by both the fungi and the ants. The group, led by Cameron Currie of the University of Wisconsin–Madison, estimates that over half of the nitrogen requirements of the system are met by these bacteria and that the colonies fertilize the surrounding soil, contributing to overall ecosystem productivity. These results highlight the importance of natural community interactions in the deconstruction of biomass, and suggest potential approaches for consolidated bioprocessing for biofuel production.

Principal Investigator

Cameron Currie
University of Wisconsin–Madison

BER Program Manager

Dawn Adin

U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]


Pinto-Tomás, A. A., M. A. Anderson, G. Suen, D. M. Stevenson, F. S. T. Chu, W. W. Cleland, P. J. Weimer, and C. R. Currie. 2009. “Symbiotic Nitrogen Fixation in the Fungus Gardens of Leaf-Cutter Ants,” Science 20(5956), 1120–3. DOI:10.1126/science.1173036.