My Top 10 Science Stories of 2006 – #6: Bacteria in Liquid Nitrogen



Living in Liquid Nitrogen

By Davide Castelvecchi
As I was reading New Scientist last August — the issue with my cover story, as it happens — I stumbled into this tale, told by my friend Douglas Fox. The tale’s hero goes by the unlikely name of Colwellia psychrerythraea 34H.

Colwellia is one of those bugs that have been found, alive and kicking, trapped down deep in the ice of Antarctica. Karen Junge, a microbiologist at the University of Washington in Seattle, was studying Colwellia in her lab’s freezers, trying to understand how it manages to survive at -20 degrees Celsius.

To check out the bug’s metabolism at those temperatures, Junge measured how fast it absorbed an amino acid compared with specimens kept at -80 degrees, where no metabolism would occur. Something was wrong, though: the metabolism of her control specimens didn’t stop. So Junge tried sticking them in liquid nitrogen. Even there, at -196 degrees, Colwellia kept eating up the amino acid, a sign that it was still biologically active.

Bugs like Colwellia raise our hopes of finding some kind of life on other solar system bodies, such as the frigid moons of Jupiter and Saturn. They also show how hard it will be for us to make sure that those bugs haven’t somehow gotten there from Earth, brought inadvertently by our spacecraft. NASA’s Department of Planetary Protection (it really exists) works hard to prevent that kind of contamination, but with bugs so small and hardy, it seems to have an almost impossible task. (“Is Life on Mars from Pasadena?” was Discover magazine’s memorable cover teaser a couple of years ago, referring to spacecraft built at Pasadena’s Jet Propulsion Laboratory.)

Besides, microbes may have been traveling by themselves aboard rocks that were ejected from our planet by the impact of some large asteroid, and some might have gotten there alive, as Selby Cull describes in her wonderful cover story in the January 2007 issue of Sky & Telescope. Paleontologists could some day go hunting for fossils on the moon. Peter Ward, another UW-Seattle scientist, suggested just that last April (also in New Scientist). Some of the rocks ejected from Earth in its early days could have ended up on the moon, carrying primordial microbes in them. Having stayed undisturbed for billions of years, these could be the earliest fossils we’ll ever find.

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