Abstracts - Ana Carolina Alves dos Santos

New Insights in the Chemical-Ecology of E. weberi and Microorganisms Associated with Leaf-Cutting Ants

Ana Carolina Alves dos Santos1,2*, Kirstin Scherlach2, Paulo Cezar Vieira1,3, Christian Hertweck 2

1 Departamento de Química, Universidade Federal de São Carlos, São Carlos, Brazil
2 Faculdade de Ciências Farmacêuticas de Ribeirão Preto, USP, Ribeirão Preto
3 Leibniz Institute for Natural Product Research and Infection Biology, HKI, Jena, Germany
* Correspondence: carol_santos15@hotmail.com

The study of microorganisms associated with insects provides unique opportunities to exploit natural antimicrobial and insecticides agents due to the chemical mediators utilized in the defensive and threat strategies. Leaf-cutting ants’ fungal garden comprises a complex symbiosis in which are involved, at least, a mutualistic fungus (Leucoagaricus gongylophorus), a specialized parasite (Escovopsis spp.), symbiont actinomycetes (Pseudonocardia and Streptomyces spp.) and other microorganisms with unknown ecology relationship. Fungi belonging to the genus Escovopsis are mycoparasites and can destroy fungal gardens completely by the secretion of antifungal and antibacterial metabolites. It is already known that E. weberi has a reduced genome in which were identified 17 putative secondary metabolite biosynthesis clusters like terpene synthases, polyketide synthases (PKS) and nonribosomal peptide synthases (NRPSs). However, the chemical machinery as well as the basis of this interaction remain unknown. Therefore, leaf-cutting ants microbiome comprises an ideal system to study the chemical-ecology of microbial interactions due to the wealth of microbial interactions described, and the lack of information on the molecules involved therein. Aiming to get some progress in the chemical-ecology of Escovopsis weberi, especially in its mode of action, we have performed some coculture and MALDI imaging experiments between the parasite and the mutualistic fungi. These experiments revealed that the interactions are even more complex: E. weberi produces some metabolites such as melinacidines as virulence factors that target the mutualist Pseudonocardia instead of L. gongylophorus. Although melinacidin showed no antifungal activity against L. gongylophorus, it displayed a MIC of 10 μg/mL and 0.5 μg/mL against two different strains of Pseudonocardia. As the population of bacteria decreases with the secretion of these substances, the nest become more susceptible to the attack of E. weberi, giving rise the infection of the fungal garden. Based on the obtained results, we conclude that these metabolites play an important role during the infection process and consequently, in the nest collapse.