Oddball Amoebas Sprout Arms When Stressed Scientists have deciphered the genome of one of Earth's strangest creatures. It turns from a lethargic amoeba into a sprightly, two-armed swimmer under stress. Its enormous number of genes allows the amoeba to morph and survive in the unforgiving mud where it lives.

Oddball Amoebas Sprout Arms When Stressed

Oddball Amoebas Sprout Arms When Stressed

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Naegleria gruberi grows a pair of flagella when under stress. But unlike a sperm tail, it puts these appendages out front, and swims by breast stroke. The organism is stained to emphasize its anatomy. Courtesy of Lillian Fritz-Laylan hide caption

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Courtesy of Lillian Fritz-Laylan

Step aside, Dr. Jekyll and Mr. Hyde. Here's a story about an organism that dramatically transforms itself when it's under stress. It turns from a lethargic amoeba into a sprightly, two-armed swimmer.

This unlikely single-celled creature is named Naegleria gruberi. It lives in the dirt, under the eucalyptus trees, on the University of California, Berkeley campus.

"A lot of people call Naegleria a soil organism, but if you look in dry, sandy soil, you won't find it," says Lillian Fritz-Laylin, a graduate student at Berkeley. "It hates to get dried out. So you'll find it in the mud, or in the pond, or in the bottom of puddles in the woods."

A Morphing, Breast-Stroking Amoeba

These days, when you want to see what makes an organism tick, you order up a scan of its genes. And as it happens, scientists at the Department of Energy's Joint Genome Institute in Walnut Creek, Calif., were sequencing a bunch of organisms, and they had a little extra room in their DNA-reading machines. So biologists at UC-Berkeley thought they'd throw in Naegleria's DNA as well, and Fritz-Laylin got put on the project.

"I started doing it, playing around, trying to figure out how to do that. And I really fell in love," she says. "You take this organism that oozes and is slow and clumsy, and basically you just stress it out, and it becomes this fast, fun, kind of bird-like organism."

It spends its days as an amoeba, lazily meandering around and eating bacteria. But when it's stressed out, it grows two long, whip-like appendages called flagella. That's right. We're talking stress-induced self-flagellation. In the mud. On the Berkeley campus.

"Instead of a sperm, like a sperm tail, it puts the flagella in front of it and swims something akin to a breast stoke," Fritz-Laylin says.

'Amazingly Complex' Single Cells

Of course, this transformation requires cobbling together a dramatically different cellular architecture to support this completely different lifestyle.

"Naegleria's pretty amazing because it can make one of these structures entirely from scratch. And it does it really fast," Fritz-Laylin says. "It can do it in an hour to an hour and a half."

She wanted to understand how that happens. And sure enough, there are clues in the organism's genes. She and her colleagues report in the journal Cell that this itty-bitty creature has 16,000 to 17,000 genes. Humans edge them out in gene count, but only by a few thousand.

That isn't all that surprising, when you think of it. "I mean, we are very complex, but when you think of it, Naegleria are amazingly complex, because they are one cell, and they do a lot of the things we do with our entire bodies," she says.

The Naegleria Family's Black Sheep

Fritz-Laylin is fascinated by Naegleria because she's trying to understand how complex cells evolved. But there may be a practical payoff, as well. Naegleria gruberi has a malicious cousin, named fowleri, that causes a rare human disease.

"It's pretty, pretty nasty. If you're swimming in water that has a lot of Naegleria fowleri and you happen to get some water up your nose, what can happen is they crawl along your olfactory [nerve fibers], so they basically go into your nose, into your brain and eat your brain. And you're dead pretty quickly."

She says nose plugs are a good idea in Naegleria-infested waters.