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.
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Oddball Amoebas Sprout Arms When Stressed

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Oddball Amoebas Sprout Arms When Stressed

Oddball Amoebas Sprout Arms When Stressed

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STEVE INSKEEP, Host:

Next, we'll hear about a student who looked at the world around her and found a somewhat less-evolved version of "Dr. Jekyll and Mr. Hyde." It's an organism that dramatically transforms itself when under stress. It turns from a lethargic amoeba into a spritely, two-armed swimmer. NPR's Richard Harris has more.

RICHARD HARRIS: This is the story of an unlikely, single-celled creature named Naegleria gruberi. It lives in the dirt, under the eucalyptus trees on the UC Berkeley campus.

M: A lot of people call Naegleria a soil organism, but if you look in sort of dry, sandy soil, you won't find it.

HARRIS: Lillian Fritz-Laylin is a graduate student at Berkeley.

M: It really hates to get dried out. So you'll find it in the mud, sort of - or in the pond, or in the bottom of puddles in the woods.

HARRIS: Now, 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 Joint Genome Institute in California were sequencing a bunch of organisms, and they had a little extra room in their DNA-reading machines. So biologists at UC-Berkeley thought, what the heck, let's throw in Naegleria. Lillian Fritz-Laylin got put on the project.

M: So I started playing around, figuring out how to do that. And I really kind of fell in love, because you take this organism that oozes and is kind of slow and clumsy and basically, you just stress it out, and it becomes this really fast, fun, sort of bird-like organism.

HARRIS: It spends its days as an amoeba, lazily meandering around and scarfing up bacteria. But when it's stressed out, it grows two long, whip-like appendages called flagella. Yep, we're talking stress-induced, self- flagellation, in the mud, on the Berkeley campus.

M: Instead of a sperm, like a sperm tail, it puts the flagella in front of it, and sort of swims something akin to a breast stroke.

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

M: Naegleria's pretty amazing because it can make one of these structures entirely from scratch. And it does it really fast, within an hour to an hour and a half.

HARRIS: Lillian Fritz-Laylin 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 organism has 16 or 17,000 genes. Humans edge them out in gene count, but only by a few thousand.

That isn't so surprising, when you think of it.

M: I mean, we are very complex, but if you think about Naegleria, it's amazingly complex, because it's one cell, and it's doing a lot of the stuff that we do with our entire bodies, right?

HARRIS: Lillian 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, and that causes a rare human disease.

M: It's pretty nasty. So they basically - 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 axon, so basically go through your nose, into your brain and eat your brain. And you're dead pretty quickly.

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

Richard Harris, NPR News.

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