Editors' ChoiceMicrobiology

Tapping Lines of Communication

Science Signaling  15 Jan 2013:
Vol. 6, Issue 258, pp. ec14
DOI: 10.1126/scisignal.2003964

Carnivorous fungi may sound like something out of a science fiction horror movie, but their existence is science fact. In the presence of nematodes, nematophagous fungi consume the worms, either internally as parasites or by creating traps to immobilize their prey and devouring the worms from the outside. A previously unknown substance secreted from nematodes induces some nematophagous fungi to form traps. Hsueh et al. identified ascarosides as the molecular trigger for trap formation. Ascarosides are a large family of related small molecules that are secreted from nematodes and act as pheromones that modulate development and behavior. When cultured in low-nutrient medium in the presence of nematodes, the fungus Arthrobotrys oligospora formed traps of adhesive hyphae. Trap formation did not occur in nutrient-rich conditions, consistent with previous reports of the fungi only adopting a carnivorous diet when nitrogen-starved. Of the 10 ascaroside compounds tested, about half induced trap formation when applied to nutrient-limited A. oligospora at concentrations typical of those observed in nematode populations. The effect of ascarosides on trap building was tested in seven additional species of nematophagous fungi, three of which are closely related to A. oligospora and form similar traps. The other four are distantly related to A. oligospora and form morphologically distinct traps. Purified ascarosides induced trap formation only in those species closely related to A. oligospora, with a different combination of ascarosides inducing maximal trap formation in each species, suggesting that fungal species may be tuned to detect prey species that emit a distinct pheromone profile. How the fungi detect the pheromones and translate these signals into a morphogenetic program remains unknown, but it is nonetheless interesting that microorganisms can eavesdrop on intraspecies communication to identify and trap prey.

Y.-P. Hsueh, P. Mahanti, F. C. Schroeder, P. W. Sternberg, Nematode-trapping fungi eavesdrop on nematode pheromones. Curr. Biol. 23, 83–86 (2013). [PubMed]