A New, Somewhat Moldy Branch On The Tree Of Life

May 12, 2011
Originally published on May 12, 2011 8:55 am

If you think biologists have a pretty good idea about what lives on the Earth, think again. Scientists say they have just now discovered an entirely new branch on the tree of life. It's made up of mysterious microscopic organisms. They're related to fungus, but they are so different, you could argue that they deserve their very own kingdom, alongside plants and animals.

This comes as a big surprise. Just a few years ago, professor Timothy James and his colleagues sat down and wrote the definitive scientific paper to describe the fungal tree of life.

"We thought we knew what about the major groups that existed," says James, who is curator of fungus at the University of Michigan. "Many groups have excellent drawings of these fungi from the last 150 years."

Many fungi are already familiar. There are mushrooms, yeasts, molds like the one that makes penicillin, plant diseases such as rusts and smuts. Mildew in your shower is one, along with athlete's foot. There are even fungi that infect insects — as well as fungi that live on other fungi.

Biologists figure they've probably only cataloged about 10 percent of all fungal species. But they thought they at least knew all of the major groups.

Oops. A paper being published in the journal Nature says that isn't so. Thomas Richards, at the Natural History Museum in London, says biologists can mostly only study microscopic fungi if they can grow them in the lab.

"But the reality is most of the diversity of life we can't grow in a laboratory. It exists in the environment," he says.

And microscopic organisms are just about impossible to find just looking at dirt or water through a microscope. So Richards and his colleagues tried more modern means.

"About 10 years ago, people started using molecular approaches," he says. "So they started targeting the DNA in the environment, specifically."

Using those techniques, they struck pay dirt. They found novel bits of DNA — related to fungi, but clearly different from all of the known varieties — just about everywhere, "including pond water, lake water, freshwater sediments and marine sediments," Richards says. "Almost everywhere we looked we found this novel group."

They then brought samples back to the lab and devised a technique to make the organisms containing this novel DNA glow under a microscope. As a result, they've managed to get a few glimpses of these mysterious life forms, which they have named cryptomycota.

"We know they have at least three stages to their life cycle," Richards says. "One is where they attach to a host, which are photosynthetic algae. Another stage ... they form swimming tails so they can presumably find food. And [there's] another stage, which we call the cyst phase, where they go to sleep."

Now, Richards and his colleagues would like to figure out how to grow them in the lab to really get to know them.

"At the moment it's a bit too early to be sure about what role they play in the environment," he says. "But one thing we can be certain of is because they're so diverse, they're probably playing many, many different roles in many different environments."

Back at the University of Michigan, Tim James says the discovery is revolutionary. It's rocking the world of fungus phylogenetics.

"It's going to be interesting because one of the controversies is going to be, are they really fungi or not?" he says.

Because they apparently lack a protein in their cell walls that is a defining feature of fungi, you could argue that they aren't actually a member of the fungus kingdom but deserve an entire kingdom of their own. And before you get too comfortable with the idea that all of these species just hang out in ponds or sediments, James adds, "there could be some human parasites in here eventually discovered."

But fret not. Mostly, fungi are doing important things, like recycling nutrients. And most of the time, they seem to leave us alone.

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STEVE INSKEEP, Host:

If you think biologists have a good idea about everything that lives on the Earth, think again. Scientists say they have just now discovered an entirely new branch on the tree of life. It's made up of mysterious microscopic organisms. They are related to fungus, but they're so different you can argue they deserve their very own kingdom, alongside plants and animals. NPR's Richard Harris reports.

RICHARD HARRIS: It was just a few years ago that Tim James and his colleagues sat down and wrote the definitive scientific paper to describe the fungal tree of life.

TIM JAMES: We thought we knew about the major groups that existed. Many books have excellent drawings of these fungi from, you know, the last 150 years.

HARRIS: James, who is curator of fungus at the University of Michigan, says of course many are familiar.

JAMES: You've got mushrooms, yeast and molds.

HARRIS: Plenty of plant diseases like rusts and smuts. There's the stuff that grows in your shower or between your toes.

JAMES: Fungi that specialize on insects - the entomopthrelis(ph).

HARRIS: A paper being published in the journal Nature says: not so. Thomas Richards, at the Natural History Museum in London, says biologists can mostly only study microscopic fungi if they can grow them in the lab.

THOMAS RICHARDS: But the reality is that most of the diversity of life we can't grow in a laboratory. It exists in the environment.

HARRIS: And microscopic organisms are just about impossible to find just looking in dirt or water through a microscope. So Richards and his colleagues tried more modern means.

RICHARDS: About 10 years ago, people started using molecular approaches. So they started to try and target the DNA in the environment, specifically.

HARRIS: Using those techniques, they struck pay dirt. They found novel bits of DNA - related to fungi, but clearly different from all the known varieties - just about everywhere.

RICHARDS: Including pond water, lake water, fresh water sediments and marine sediments. Basically, almost everywhere we looked we found this novel group.

HARRIS: They then brought samples back to the lab and devised a technique to make the organisms containing this novel DNA glow under a microscope. So they've managed to get a few glimpses of these mysterious life forms, which they've named cryptomycota.

RICHARDS: And we know that they have at least three stages to their lifecycle. One is where they attach to a host, which we think are photosynthetic algae. Another stage where they form swimming tails so they can presumably find food. And another stage, which we call the cyst phase, where they go to sleep.

HARRIS: Now Richards and his colleagues would like to figure out how to grow them in the lab to really get to know them.

RICHARDS: At the moment it's a bit too early to be sure about what role they play in the environment. But one thing we can be certain of is that because they are so diverse, they're probably playing many, many different roles in many different environments.

HARRIS: Back at the University of Michigan, Tim James says the discovery is revolutionary. It's rocking the world of fungus phyologenetics.

JAMES: It's going to be interesting because one of the controversies is going to be: Are they really fungi or not?

HARRIS: Since they apparently lack a protein in their cell walls that is a defining feature of fungi, you could argue that they aren't actually a member of the fungus kingdom, but deserve an entire kingdom of their own. And before you get too comfortable with the idea that all these species just hang out in ponds or sediments...

JAMES: There could be some actually human parasites in here eventually discovered.

HARRIS: Richard Harris, NPR News.

(SOUNDBITE OF MUSIC)

INSKEEP: A little fungus music on NPR News. Transcript provided by NPR, Copyright NPR.