Ammonia Production by Symbionts of Leaf-Cutting Ants Strongly Inhibits the Fungal Pathogen .

Leaf-cutting ants live in mutualistic symbiosis with their garden fungus that can be attacked by the specialized pathogenic fungus . symbionts from leaf-cutting ants contribute to protect against pathogens. The symbiont sp. Av25_4 exhibited strong activity against in co-cultivation assays. Experiments physically separating and sp. Av25_4 allowing only exchange of volatiles revealed that sp. Av25_4 produces a volatile antifungal. Volatile compounds from sp. Av25_4 were collected by closed loop stripping. Analysis by NMR revealed that sp. Av25_4 overproduces ammonia (up to 8 mM) which completely inhibited the growth of due to its strong basic pH. Additionally, other symbionts from different ants inhibited by production of ammonia. The waste of ca. one third of and leaf-cutting ant colonies was strongly basic due to ammonia (up to ca. 8 mM) suggesting its role in nest hygiene. Not only complex and metabolically costly secondary metabolites, such as polyketides, but simple ammonia released by symbionts of leaf-cutting ants can contribute to control the growth of that is sensitive to ammonia in contrast to the garden fungus .