Horror: Bacteria-Controlled Fungus That Eats Worms from the Inside Out

A worm might die in all sorts of awful ways. There's being swallowed alive by a bird, for one, and then there are bored proto-sadist children with magnifying glasses. Is there any creature on Earth more likely to perish under a shoe? Probably not. It just gets worse from there, according to a ​new paper from biologists at China's Yunnan University, with the worms' primary prey deploying a fully awful defense courtesy of some bystanding fungus.

Nematodes already have a gruesome foe in this particular species, A. oligospora. Said fungus has two main life cycles, the second of which reduces to "horri​bly killing worms." Simply, a worm cruising around this or that patch of cow shit might become ensnared in a constricting ring deployed by the fungus and, once entrapped, the fungus proceeds to grow into the worm where it goes to town, digesting its prey from the inside out.

There is a chemical trigger that turns A. oligospora into its predatory version. Urea, a chemical present in cow dung (and urine), breaks down into ammonia, which acts as the chemical signal the fungus needs to start forming its worm-traps. Dinnertime, slowly.

Nematodes aren't quite so innocent in all of this, at least those characterized as bacterivorous. Their proactive role is in the consumption of various bacteria, particularly those growing on or around the aforementioned dung.

As the Yunnan team puts it, bacteria and nematodes exist in a sort of "arms race," with bacteria evolving new anti-worm toxins and deterrents, while worms evolve not to be bothered by those toxins and deterrents. "For example," they write, "nematodes have evolved to avoid the toxic/pathogenic bacteria and forage for nontoxic bacteria to support their growth and reproduction." So what do the nontoxic bacteria do?

They outsource. Of the 126 bacterial colonies explored by the researchers, three were found to be highly-efficient at inducing trap-formation among the A. oligospora. Curiously, it appears as though the signaling pathway used by the bacteria to prompt the fungal response is different from the usual one used by the fungus to detect nematode prey.

So that's a thing that happens and it's grotesque obviously, but also kind of amazing. The bacteria are essentially using hired hitmen to take out their rivals, chemically. At least for the time being: Nature has a way of out-clevering herself.