Leaf-cutting ants (Formicidae: Attini) are capable of devouring enormous amounts of vegetation - about 20 percent of the fresh-leaf biomass in the Neotropics. This makes agriculture of non-native plants which have not evolved a form of protection against predation by the ants, such as fruit trees from California or Africa, impossible in the areas where these ants prevail. The ants use this vegetation to feed fungal mutualists on which they themselves feed. The fungal mutualists= gardens are infected with a parasitic microfungus Escovopsis (Ascomycota: anamorphic Hypocreales), which is highly virulent and has the potential to rapidly devastate the garden. It is prevented from doing so by a third mutualist, an actinomycete (filamentous bacterium) of the genus Streptomyces, which produces an antibiotic which keeps the Escovopsis under control. The experiments described below will be carried out in an attempt to find a streptomycin-resistant form of Escovopsis which can be used to help destroy ant fungus gardens so that agricultural projects can succeed in regions where they are prohibited by the destructive effects of the leaf-cutting ants. A streptomycin-resistant form of the microfungus could be used as a soil pretreatment, blockade, or plant spray to protect against attack by these ants. Knowledge gained by studying antibiotic production by actinomyces, and antibiotic resistance by microfungi may provide some useful data for the study of antibiotic resistance in man, which is becoming a major problem with the overuse of known antibiotics for minor ailments.
Fungus farming by attine ants predates human agriculture by about 50 million years (Mueller, Rehner and Schultz, 1998). The ants live symbiotically with the fungi because the particular fungi they cultivate can break down fresh leaves into nutrients which the ants can use (Angier, 1994). The ants literally feed the leaves to the fungi, which, in their turn, metabolize t...