Speaker
Description
Fungi of the subphylum Mortierellamycotina occur ubiquitously in soils where they play pivotal roles in carbon cycling, xenobiont degradation, and promoting plant growth. These important fungi are, however, threatened by micropredators such as fungivorous nematodes, and yet little is known about their protective tactics. We have found that Podila verticillata shields itself from fungivorous nematodes with the help of toxin-producing bacterial endosymbionts. We provide evidence that the highly cytotoxic macrolactones (CJ-12,950 and CJ-13,357, syn. necroxime C and D), which were believed to be fungal metabolites, are in fact produced by a previously overlooked bacterial endosymbiont, Candidatus Mycoavidus necroximicus. Using the model organism Caenorhabditis elegans and the fungivorous nematode Aphelenchus avenae, we probed the anthelmintic activity of the necroximes and demonstrated the effective host protection in cocultures of nematodes with symbiotic and chemically complemented aposymbiotic fungal strains. Additionally, we discovered a novel cyclic lipodepsipeptide (symbiosin) produced by the endosymbionts, which synergizes with necroximes and boosts anthelmintic activity. This study reveals an important function for endofungal bacteria as producers of protecting agents and opens the possibility for the development of new biocontrol agents.
