Acromyrmex leafcutter ants form a tripartite symbiosis with the fungal cultivar Leucoagaricus gongylophorus and Pseudonocardia bacteria. Ants provide leaves as growth substrate for the fungus and the fungus provides the sole food source for ant larvae. The bacteria produce molecules that protect the cultivar against pathogens, such as the fungal parasite Escovopsis weberi. Two studies show that E. weberi produces secondary metabolites during infection of the cultivar that promote the collapse of the fungus garden in leafcutter ant colonies. Heine et al. identified melinacidin IV and the terpene-indole alkaloid shearinine D, both of which kill Pseudonocardia species. Ingestion of shearinine D by ants adversely affects their behaviour and results in ant death. Dhodary et al. showed that E. weberi produces shearinine L and shearinine M, as well as emodin and cycloarthropsone, which inhibit the growth of L. gongylophorous.
Heine, D. et al. Chemical warfare between leafcutter ant symbionts and a co-evolved pathogen. Nat. Comms. 9, 2208 (2018).
Dhodary, B. et al. Secondary metabolites from Escovopsis weberi and their role in attacking the garden fungus of leaf cutting ants. Chem. Eur. J. 24, 4445–4452 (2018)