Microbes Survive tremendous Squashing

Posted by Mike Kremer on Feb 23, 2002 at 21:38

Journal Reference Science (vol 295
also Referenced in New Scientist, 21 February '02

Life could exist at extreme and uncharted depths on apparently barren alien planets, say US researchers.
New research shows that common Earth bacteria can survive pressures equivalent those found 50 kilometres beneath the Earth's crust or 160 kilometres under water. No organisms have ever been shown to be capable of withstanding such colossal pressure before.

"We shouldn't rule out the possibility of life [on other planets], even if it isn't found on the surface," says researcher Anurag Sharma at the Carnegie Institution in Washington, US.

Dave Roberts at the Natural History Museum in London, UK, agrees, stating that no organisms have ever been subjected to such extreme experimental pressures before, but thinks the findings are not surprising.
Sharma and fellow researcher James Scott, subjected two common species of bacteria, E. coli and Shewanella oneidensis, to extreme pressures using a diamond anvil cell. This device is normally used to test material behaviour at high pressures by applying a high force to a tiny area - between two diamonds.
The activity of the bacteria under pressure was watched by using a molecular spectroscope to monitor the bacteria's rate of food consumption in the experimental capsule. Formate, a compound derived from formic acid, is converted into CO2 and hydrogen to produce energy by the bacteria.

Even under extreme pressure, the bacteria were found to continue consuming the formate. The researchers ruled out other possible explanations for the disappearing formate by using two sets of control bacteria, one killed with heat and one poisoned with cyanide, which slows down its metabolism.
Sharma admits that further research is needed to fully understand how the bacteria can function at this pressure.
He adds that life forms may yet be found at unexplored depths on Earth, and beneath the surface of Solar System bodies such as Jupiter's moons Europa, Callisto and Ganymede.
Europa's oceans are probably deeper than those on Earth, at up to 100 kilometres. But Roberts states that their gravity is less, and he estimates that the pressure at the bottom of Europa's oceans may be equivalent to just six kilometres under the Earth's seas.

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