Ecology: War of the worms, bacteria and fungi

A bacterial metabolite, urea, induces a lifestyle change in certain soil fungi causing them to trap and eat nematodes, reports a study published online this week in Nature Communications. This research suggests that urea release may be a strategy used by soil bacteria for ‘mobilizing’ fungi for their own benefit in order to get rid of the bacteria-hunting nematodes.

Certain fungi form specialised cellular structures or 'traps' to feed on nematodes (a type of worm). These traps are usually produced when certain nematodes are near the fungi, as the worms release characteristic compounds (ascarosides) that the fungi recognize and respond to. This induces the fungi, which normally feed on dissolved organic matter, to eat the nearby nematodes. However, the traps are also formed in response to previously unknown compounds present in cow dung.

Ke-Qin Zhang and colleagues hypothesized that at least some of the unknown compounds could be originating from the many bacteria living in cow dung. After analysing the metabolites released by bacteria, they found that one of them, urea, induced trap formation in fungi and that certain bacteria in cow dung were particularly good at producing and releasing the compound. The researchers also discovered urea triggered trap formation through a mechanism that was different from that triggered by ascarosides. While this research suggests an interaction between bacteria and fungi, further research is needed to confirm and clarify this relationship.