Many antibiotics are derived from natural environments, but we know little about the ecological function of most of these molecules. Trachymyrmex ants of the American Southwest and their microbial associates form an ideal system for interrogating antibiotic function in nature. The fungus-growing ants in this niche are postulated to participate in a mutualistic relationship in which bacterial symbionts protect the ants’ fungal cultivar from pathogenic fungi in return for nutrients from the ants. Amycolatopsis strain 17SM-8, isolated from the cuticle of the ant Trachymyrmex smithi, antagonizes the fungal pathogen of the ants’ colonies, and we wanted to understand the chemical basis for that antagonism. Using bioassay guided fractionation, we have established that the molecule responsible is the antibiotic ECO-0501. We have confirmed the identity of the molecule by comparison to an authentic standard using LC-MS/MS. This molecule’s antibacterial activity had previously been documented, but this is the first report to our knowledge of its antifungal activity. The discovery of ECO-0501, an antibiotic that previously had no known ecological function, suggests Amycolatopsis as an effective defensive microbial associate.

Identification of an antibiotic produced by ant-associated amycolatopsis bacteria

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ACS Fall 2022

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