Archive for the ‘Biology’ Category

Meet Kristopher Schwebler, NASA Goddard summer intern and water bear wrangler. Could the Japanese movie monsters of the moss world hold the key to putting astronauts in suspended animation?

August 11th, 2010 1 comment
Run for your lives! Water bears!

Run for your lives! Water bear!

Meet Kristopher Schwebler, Goddard Space Flight Center’s first water bear wrangler. But he doesn’t teach them the usual circus tricks, like riding a little bicycle around the ring or balancing beach balls on their noses. He’d be happy if the little guys just didn’t all drop dead.

Before the rumors start to fly on the Internet that Goddard is littered with cute furry carcasses, be advised that water bears — a.k.a., moss piglets, from the phylum Tardagrada — are actually tiny critters that live in tree stumps and just about everywhere else on Earth. Many species of tardigrades are microscopic, but the biggest, chubbiest adult tardigrade barely breaks a millimeter in length. Many species would fit comfortably in the period at the end of this sentence. The name tardigrade means “slow walker,” a reference to their bearlike lumbering gate.

Kristopher Schwebler

Kristopher Schwebler

Scientists study tardigrades because they have this amazing ability to come back to life after drying out (“desiccating”) and going into a kind of bulletproof suspended animation called cryptobiosis.
And while they are hibernating, they can survive:

1)  temperatures as low as absolute zero (-273°C) and as high as 151°C.

2)  pressures as high as 5921 times Earth’s atmosphere and as low as the vacuum of space.

3)  1000 times more gamma irradiation than humans can withstand.

In short, they are as unkillable as Twinkies (albeit very tiny Twinkies).

Gathering moss at the stump . . .

Gathering moss at the stump . . .

Understanding how they pull of this trick could show us the way — as in “way in the future” — to putting astronauts in suspended animation for extended space journeys. Or lead to better methods for preserving transplantable tissue and organs — maybe entire hearts or kidneys.

playa PR buttonFrozen alive
Kris was a summer intern in the Lunar and Planetary Science Academy. (He finished up August 6.) He holds a B.S. in genetics, cell biology, and development from the University of Minnesota-Twin Cities as well as a B.A. in physiology and minors in Spanish Studies and Global Studies. He starts this fall at Weill Cornell Medical School in New York City. Did I mention he plays the French horn and trumpet in various ensembles?

Well, OK, very smart guy. But my favorite part of the Clever and Promising Young Intern bio is his explanation of why he ended up doing research on water bears at Goddard Space Flight Center: “I have always wondered how blobs of molecules somehow effortlessly come together to create life.”

Chips of moss containing tardigrades . . .

Chips of moss containing tardigrades . . .

Bear hunt
Kris’s mission as an LPSA intern was to assess the ability of water bears to be frozen alive and then revived — you know, like the intra-galactic-traveling astronauts in countless sci-fi flicks.  As part of this, he would develop a reliable supply of water bears, ideally by learning how to breed them like colonies of lab mice.

But first, he needed breeding stock — a sort of tardigrade sourdough starter. This proved surprisingly difficult and consumed much of Kris’s 10-week internship.

He worked on the project in June and July under the supervision of Goddard planetary scientist Gunther Kletetschka. And by the way, don’t miss the Goddard web feature today by Elizabeth Zubritsky about the Lunar and Planetary Science Academy trip to study the sailing stones of Racetrack Playa in Death Valley, California. Kletetschka went on that trip, along with Kris and the other LPSA interns.

Just add water . . .

Just add water . . .

But back to Kris. He needed some water bears to work with, so Dr. Kletetschka asked for help from a NASA researcher, Daiki D. Horikawa of the Ames Research Center in Moffet Field, California. He’s a tardigrade wrangler/breeder/researcher extraordinaire, and he kindly mailed some desiccated water bears through the mail. Kris added water….. and waited.

The first batch came back to life but would not breed, and expired after their several-days life cycle. Or they didn’t wake up at all.

Water bears are also called moss piglets because they are found in moss. So Kris walked a few hundred feet into a wooded area at Goddard and sliced a bunch of moss and lichens from a true stump. He added water, waited, and voila! “I just added water to them an they came out swimming around.”

A home for water bears . . .

A home for water bears . . .

It’s harder to collect these little guys than it sounds. He must examine the petri dish full of mushy moss under a microscope and use a syringe to capture the water bears. He attempted to feed them/breed them in a see-through plastic container in which he cultivated green algae for the water bears to feed on.

They all died.

Even though the world is just filthy with tardigrades, the little critters are fussy. Different species have different needs. And let’s not even bring up what it takes to coax water bear females into laying eggs so that males can fertilize them. It’s harder than stand-up comedy.

But science marches on. One morning the last week of Kris’s internship, I accompanied him on a final pilgrimage to the Goddard water bear park, otherwise known as “the stump behind Building 2.”

“This is how I do it,” he said, pulling out a razor blade and carefully slicing off chunks of moss from the stump, tucking it into a plastic petri dish. A hundred yards south of our position, the traffic on Greenbelt Road zoomed by the perimeter fence, oblivious to the water bear hunt amidst the scrub oak.

Gunther Kletetschka stops by the lab . . .

Dr. Kletetschka stops by . . .

Lab work
The next day, we met again at the lab — a cluttered garagelike space out at Goddard’s Magnetic Test Facility. Several other LPSA interns flitted about, preparing their final presentation for the coming Friday.

The moss had gotten a good overnight soak, and Kris began collecting tardigrades. The plan was to freeze them solid in liquid nitrogen and take them over to Goddard’s scanning electron microscope to image them.

Tardigrades, it turns out, produce a special kind of sugar molecule called Trehalose. It appears to suppress the formation of tissue-tearing large ice crystals. As I watched Kris work, LPSA intern Leva McIntire used liquid nitrogen to freeze a solution containing Trehalose to determine its anti-icing effect.

Earlier that day, Kris had frozen a bunch of tardigrades very quickly in an attempt to prevent extensive ice crystal formation, producing “semi-amorphous ice.” Then he thawed them. One, he suspected, had come back to life. But he wasn’t sure.

Kris at the microscope . . .

Kris at the microscope . . .

If true, this would be significant. Normally, scientists allow tardigrades to dry out before freezing them, or bombarding them with gamma rays, or performing other acts of torment to find out what can stand. Direct freezing would be a true test of tardigrade toughness.

I watched as Kris pursued water bears with his syringe, and he was having a hard time catching them. “It can be very tedious,” he said. “On a good day, I’ll get 20 after looking for a few hours. But those are just the ones you can see,” Kris said.

Meanwhile, Dr. Kletetschka came by to check on Kris and the other interns at the lab. He explained that secret to tardigrade toughness is the suite of genes that allow them to repair a biological insult known as double-strand DNA breaks.

In our bodies, DNA suffers damage all the time. But our cells have tiny repair crews to fix it.

When a tardigrade dries up — or when it freezes solid — its tissues sustain damage. Entire DNA molecules break. But they appear to be able to fix it. The details are not all exactly clear, but the ability to repair such major damage is of keen interest to scientists.

As we talk, Gunther flips into self-described “science fiction” mode. What if we could develop a genetic engineering technique to confer the tardigrade repair system on humans? One that might allow astronauts to repair space radiation damage?

Intern Leva McIntire pours liquid nitrogen . . .

Intern Leva McIntire pours liquid nitrogen . . .

Freeze dried
It was getting late in the afternoon, and Kris was still struggling to capture a water bear in his syringe and squirt it out in a single droplet on a little copper disk in a Styrofoam container. Freezing the droplet rapidly could fix the biological sample in a rigid state, avoiding other, more involved processes needed for traditional fixation.

Slowly, the surfaces of the ice droplet would boil off (sublime) in the vacuum chamber until the tardigrade’s body was exposed at the surface. At that moment, the “cryo-fixed” critter could be bombarded with electrons and imaged in all its Japanese-monster-movie splendor.

After a long weekend, after Kris moved home and got back online, I reached him. And he gave me a quick update, as well as his final presentation.

“One final conclusion of the experiment was that after flash freezing in their non-desiccated form, at least two tardigrades showed some (although minimal) signs of life, indicating they possess some mechanism to prevent damage from freezing, as almost all other organisms would die,” he emailed me.

Freze-dried water bear . . .

Freeze-dried water bear . . .

“Additionally, we developed a new way to image tardigrades with the scanning electron microscope using flash freezing and subsequent sublimation of ice within the vacuum chamber. Though our results weren’t perfect, I think with more experimentation we could use this method to avoid the shriveling seen in biological samples due to dehydration.”

It intrigues me to think what will become of Kristopher Schwebler. He says he wants to go into aerospace medicine and become a surgeon. But you never know. Could this syringe-wielding medical student become the world’s greatest water bear cowboy?

OH AND DID I MENTION? All opinions and opinionlike objects in this blog are mine alone and NOT those of NASA or Goddard Space Flight Center. And while we’re at it, links to websites posted on this blog do not imply endorsement of those websites by NASA.