Leaf-cutter ants are one of the most fascinating organisms you encounter in the tropical rain forest. Watching a river of little leaf pieces bobbing and weaving along a little path only to disappear underground is an amazing sight. Most people assume leaf-cutter ants are herbivores, plant-eaters, but no, they are fungivores, fungus eaters, and the leaves are used to raise their fungi. Like any other "garden" a fungus garden can get infected and weedy fungi can sprout up. The ants, like all big organisms, harbor an internal community of symbiotic bacteria, and unlike disease organisms, these are part of their biology. You don't like to think about this but you harbor more bacteria within you body than you have cells making up your body. A recent study has found that Streptomyces is one such ant symbiotic bacterium, and just as the name suggests, it can make antibiotics and antifungals used to stop infections and weeds from damaging the crop of fungus. This doesn't surprise me at all because one of our students on our most recent rain forest ecology field trip conducted a nice little experiment that demonstrated that extracts of leaf-cutter ants have strong antibiotic properties. Here's a link for more information on leaf-cutter ants.