Barophiles are organisms, both macroscopic and microscopic, also known as piezophiles, that thrive in environments where the pressure is unusually high, for example, deep in the ocean or far underground. Three categories of microbes found in high-pressure environments can be distinguished. Barotolerant microbes are found in the ocean to depths of 4 kilometers (about 400 atmospheres) but grow better at 1 atmosphere. Barophilic species occur at 5 to 6 kilometers and grow better at high pressure (500 to 600 atmospheres) than low. Extreme barophiles live at great depths where the pressure is at least 700 atmospheres and will not grow at all at 1 atmosphere.
In 2002, A. Sharma and colleagues observed physiological and metabolic activity of Shewnella oneidensis strain MR1 and Escherichia coli strain MG1655 at pressures of 68 to 1680 MPa in diamond anvil cells. Also, R. M. E. Mastrapa and co-workers, in 2001, published the results of their tests on Deinococcus radiodurans and Bacillus subtilis that involved exposing these microbes to extreme acceleration (4.5 × 105 m/s2) in a compressed-air pellet rifle; they noted survival rates between 40 and 100 percent.
1. Sharma, A., Scott, J. H., Cody, G. D., Fogel, M. L., Hazen, R. M.,
Hemley, R. J., and Huntress, W. T. "Microbial activity at gigapascal
pressures." Science, 295: 1514-1516 (2002).
2. Mastrapa, R. M. E., Glanzberg, H., Head, J. N., Melosh, H. J., and Nicholson, W. L. "Survival of bacteria exposed to extreme acceleration; implications for panspermia." Earth and Planetary Science Letters, 189: 1-8 (2001).