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High pressure: Bacteria survive inside diamond anvil
  

 

Squeezed in an 'anvil' between two diamonds, two species of microbes have shown scientists that they are able to survive under harsh conditions that are more likely to be found on distant planets than on the Earth's surface.


Microbial activity and viability in ice-VI. View larger

The researchers used a device called a 'diamond anvil cell' to expose samples of Shewanella oneidensis and Escherichia coli to pressures about 16,000 times greater than typical sea-level pressure. These conditions were similar to pressures that exist about 50 kilometers (30 miles) under the Earth's crust or beneath a 160-kilometer column of seawater.

About 1 percent of the microbes survived under these conditions for 30 hours, according to the findings published in Science. Given this result, the microbes might also be able to withstand the sort of high-pressure environments found in the Earth's deep subduction zones or on Jupiter's moons Europa, Callisto and Ganymede.

The team—led by geochemist Anurag Sharma and microbiologist James Scott of the Geophysical Laboratory of the Carnegie Institution in Washington, D.C.—used molecular spectroscopy to study the bacteria, which existed in a layer of water between the two diamonds. The monitoring revealed that the microbes continued metabolic activity under pressure and had limited mobility.

Future studies will have to address other aspects of life under extreme conditions. It is not yet known whether S. oneidensis (which breaks down metals) and E. coli (which lives in the human gut) can reproduce under such high-pressure conditions or withstand the extreme temperatures that might accompany the pressure.

"One of the fundamental questions that needs to be asked now is whether the response exhibited by the bacteria is due to adaptation or selection," Scott is quoted as saying. "Our results raise important questions about the impact of pressure on the evolution of life."

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Sharma, A. et al. Microbial activity at gigapascal pressures. Science 295, 1514-1516 (February 22, 2002).
 

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