from Desert Specialist Fungus-Growing Ants Suppresses Contaminant Fungi Using the Antibiotic ECO-0501.

Symbiotic help fungus-growing ants suppress fungal pathogens through the production of antifungal compounds. ants of the southwest desert of the United States inhabit a unique niche far from the tropical rainforests in which most fungus-growing ant species are found. These ants may not encounter the specialist fungal pathogen known to threaten colonies of other fungus-growing ants. It is unknown whether associated with these ants antagonize contaminant fungi and, if so, what the chemical basis of such antagonism is. We find that and strains isolated from three desert specialist species do antagonize diverse contaminant fungi isolated from field-collected ant colonies. We did not isolate the specialist fungal pathogen in our sampling. We trace strong antifungal activity from isolates to the molecule ECO-0501, an antibiotic that was previously under preclinical development as an antibacterial agent. In addition to suppression of contaminant fungi, we find that this molecule has strong activity against ant-associated and may also play a role in bacterial competition in this niche. By studying interspecies interactions in a previously unexplored niche, we have uncovered novel bioactivity for a structurally unique antibiotic. Animal hosts often benefit from chemical defenses provided by microbes. These molecular defenses are a potential source of novel antibiotics and offer opportunities for understanding how antibiotics are used in ecological contexts with defined interspecies interactions. Here, we recover contaminant fungi from nests of fungus-growing ants of the southwest desert of the United States and find that they are suppressed by isolated from these ants. The antibiotic ECO-0501 is an antifungal agent used by some of these bacterial isolates. This antibiotic was previously investigated in preclinical studies and known only for antibacterial activity.