from Fungus Gardens of Fungus-Growing Ants Produces Antifungals That Inhibit the Specialized Parasite .

Within animal-associated microbiomes, the functional roles of specific microbial taxa are often uncharacterized. Here, we use the fungus-growing ant system, a model for microbial symbiosis, to determine the potential defensive roles of key bacterial taxa present in the ants' fungus gardens. Fungus gardens serve as an external digestive system for the ants, with mutualistic fungi in the genus converting the plant substrate into energy for the ants. The fungus garden is host to specialized parasitic fungi in the genus . Here, we examine the potential role of spp. that occur within ant fungus gardens in inhibiting We isolated members of the bacterial genera and from 50% of the 52 colonies sampled, indicating that members of the family are common inhabitants in the fungus gardens of a diverse range of fungus-growing ant genera. Using antimicrobial inhibition bioassays, we found that 28 out of 32 isolates inhibited at least one strain with a zone of inhibition greater than 1 cm. Genomic assessment of fungus garden-associated indicated that isolates with strong inhibition all belonged to the genus and contained biosynthetic gene clusters that encoded the production of two antifungals: burkholdine1213 and pyrrolnitrin. Organic extracts of cultured isolates confirmed that these compounds are responsible for antifungal activities that inhibit but, at equivalent concentrations, not spp. Overall, these new findings, combined with previous evidence, suggest that members of the fungus garden microbiome play an important role in maintaining the health and function of fungus-growing ant colonies. Many organisms partner with microbes to defend themselves against parasites and pathogens. Fungus-growing ants must protect spp., the fungal mutualist that provides sustenance for the ants, from a specialized fungal parasite, . The ants take multiple approaches, including weeding their fungus gardens to remove spores, as well as harboring spp., bacteria that produce antifungals that inhibit In addition, a genus of bacteria commonly found in fungus gardens, , is known to produce secondary metabolites that inhibit spp. In this study, we isolated spp. from fungus-growing ants, assessed the isolates' ability to inhibit spp., and identified two compounds responsible for inhibition. Our findings suggest that spp. are often found in fungus gardens, adding another possible mechanism within the fungus-growing ant system to suppress the growth of the specialized parasite .