Termites are quite curious insects. Beside having social structures and building strong and sophisticated nests, some species practice fungiculture. They feed on the fungi Termitomyces, which they farm in gardens maintained by the excrement of the insects.  Nevertheless, as any garden, Termitomyces farming can suffer the invasion of  oportunistic weeds, especially the fungi Pseudoxylaria sp. Pseudoxylaria outcompetes other oportunistic fungi and Termitomyces itself when the garden is not healthy.

The group of Christine Beemelmans, from the Hans-Knöll Institute in Jena, saw in this peculiar ecosystem the oportunity to investigate the chemical weapons used by Pseudoxylaria to fight against other fungi in termite mounds. They collected a strain of Pseudoxylaria sp from a termite colonie in South Africa, and challenged it against Termitomyces and other fungi in one-to-one encounters. Pseudoxylaria inhibited the growth of all of them.

Moreover, Pseudoxylaria seemed to exudate more droplets (a process called "guttation") in close proximity to its competitor. The droplets contained several compounds, in high abundance, whose molecular mass had not been reported before. The localization of these compounds on the droplets was also visualized by MALDI - Imaging MS.



In total, six new compounds could be found in the droplets produced by Pseudoxylaria in the competition tests, called pseudoxylallemycins. Pseudoxylallemycins have two interesting structural features: they are cyclic peptides (a chain of aminoacids linked to form a ring), and they contain allene moieties (a carbon linked to two adjacent carbons by two double bonds). These features make pseudoxylallemycins very interesting as potential drugs. In fact, Beemelmans' group proved that pseudoxylallemycins have antimicrobial activity against human pathogen (like Pseudomonas aeruginosa and Mycobacterium vaccae) and are cytotoxic.



Surprisingly, pseudoxylallemycins were tested directly on the fungi grown in termite gardens, and they show no negative effect on them. It seems that Pseudoxylaria still hides antifungal metabolites, yet to be discovered.

Read the full article: 
Guo, H., Kreuzenbeck, N. B., Otani, S., Garcia-Altares, M., Dahse, H. M., Weigel, C., ... & Beemelmanns, C. (2016). Pseudoxylallemycins A–F, Cyclic Tetrapeptides with Rare Allenyl Modifications Isolated from Pseudoxylaria sp. X802: A Competitor of Fungus-Growing Termite Cultivars. Organic Letters.

Check Christine Beemelmans' research on termite gardens in this video.