When Threatened By Worms, Bacteria Summon Killer Fungi

Ed Yong in Not Exactly Rocket Science:

When you’re the size of a human, you worry about lions and tigers and bears. But if you’re a bacterium, a tiny nematode worm, just a millimetre long, can be a vicious predator. Nematodes are among the most common animals on the planet, and many of them hunt bacteria in soil and water. The microbes, in turn, have evolved many defences. Some secrete toxins. Others gather in large, invulnerable swarms*.

Now, a team of Chinese scientists have discovered the most outlandish strategy yet: some bacteria transform fungi into worm-killers.

Fungi aren’t known for their speed or mobility, but around 200 species have evolved ways of killing nematodes nonetheless. They use traps, including sticky nets and microscopic lassos made of single coiled cells. Once they ensnare a worm, they grow into it and digest it from the inside out.

These fungi aren’t always killers. One of the most common and best-studied species—Arthrobotrys oligospora—usually feeds on decaying vegetation. It only produces its deadly traps when nematodes are around. Two years ago, one team of scientists showed that it knows when to do this because it can smell its prey, detecting chemicals that the worms can’t help but produce.

But these chemicals aren’t always necessary. Earlier studies have shown that the fungi can also change from death-eaters to death-bringers when they’re exposed to fresh cow dung. Xin Wang, Guo-Hong Li, and Cheng-Gang Zou from Yunnan University reasoned that bacteria in the dung were responsible.

More here.