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.