Carnivorous Mushroom Kills With 'Cookie Cutters'

Mushrooms look like peaceful things, minding their own business as they soak up valuable nutrients from the soil around them. However, a rare few kinds of mushrooms are secret killers, lacerating, poisoning, or even strangling hidden prey as they innocently stand around. Now researchers have determined that one of these silent assassins gets the job done with nanoscopic "cookie cutters."

That's at least according to a study recently published in the journal PLOS Biology, which details how the Pleurotus ostreatus fungus attacks its prey with a toxin made up of specialized killer proteins called pleurotolusin.

P. ostreatus, commonly called the oyster mushroom, is a relatively beautiful and frilly white mushroom that is both common around the world and edible for humans. It's then no small wonder that it also happens to be one of the very few (about 0.5 percent of all) mushroom species that attack non-plant life like worms and bacteria for nutrients.

Its weapon of choice, pleurotolusin, seems to be just one of the crowd at first. A protein that's water-soluble, it normally aimlessly floats around in the nanoscopic world. However, this all changes when the protein runs into a cell membrane. Individual molecules of these proteins can group up when encountering an obstacle, combining in a ring of 13 to form what is best described as a cookie cutter.

And that unlucky 13 spells trouble for the encountered cell. Each molecule in the rings, normally tightly wound, begins to unfurl and physically push their way through the cell membrane to get inside. If the damage caused - an 8 nanometer-wide hole - isn't enough to kill the cell, the resulting infections from other molecules that would never otherwise find their way in, surely will.

You can watch a stunning motion graphic of the process here.                                                  

The resulting cell deaths can eventually kill an entire small organism, leaving it to decay around P. ostreatus, which can then soak up its nutrients.

For the most recent study, researchers slowed this entire "cookie cutter" process, recording each step in extreme detail.

They note in their work that understanding such processes is important because another version of pleurotolusin - perforin - is produced by components of the human immune system to battle infection. Knowing how to halt the process could eventually help experts prevent harmful autoimmune conditions in which the body mistakenly attacks itself.

Still, experts admit that they are a long way from understanding the process entirely, especially in creatures other than fungi.

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