Antifungal diketopiperazines from symbiotic fungus of fungus-growing ant Cyphomyrmex minutus

The attine fungus Tyridiomyces formicarum, the symbiont of the fungus-growi ng ant Cyphomyrmex minutus, produces several antifungal dikeropiperazines. This represents the first identification of antifungal compounds from an at tine symbiont and contradicts previous suggestions that attine fungi do not produce metabolites with antifungal activity. T. formicarum probably produ ces antifungal compounds in defense (1) against other fungi that invade the gardens and escape the weeding activity of the ants, or (2) against ant-pa thogenic fungi that could harm the host ants. Fungi cultivated by fungus-gr owing ants may represent a rich source of additional bioactive metabolites.