Piezophiles

A Aristides Yayanos, University of California San Diego, San Diego, CA, USA

Published online: December 2008

DOI: 10.1002/9780470015902.a0000341.pub2

Full Article on Wiley Online Library

Piezophilic bacteria (piezophiles) are adapted to high pressures and are prominent among the inhabitants of the cold deep ocean below depths of approximately 2000 m. Whereas their maximum growth rate is close to the upper limiting growth temperature, it is also at a pressure close to that of their deep-sea habitat. In contrast, bacteria in the upper 2000 m of the ocean and in terrestrial habitats have their maximum growth rate at atmospheric pressure. The PTk-diagram for a bacterium shows clearly how the temperature and pressure of its habitat influences its growth rate and allows for comparing organisms from habitats of disparate temperatures and pressures. Laboratory studies of higher organisms from the very deep ocean are rare. At the present time, research on piezophiles offers the best opportunity for learning about biochemical and molecular biological adaptations essential for all life in the deep sea and possibly in extraterrestrial settings.

Keywords: Piezophiles; pressure; bacteria; adaptation; extreme environment

	Figure 1. A PTk-diagram for bacterial isolate MT41. The pressure where it grows fastest is close to its habitat pressure of 103 MPa. In contrast, it grows fastest at a temperature of 8–10 K above its habitat temperature of 275.48 K. Isolate MT41 is an example of a hyperpiezopsychrophile. It is also an example of a piezophile. The pressure, P, is given here in bars where 1 bar=0.1 MPa. Modified from Yayanos (1986).
	Figure 2. Two growth curves of isolate MT41. The lower curve is growth at 34.6 MPa and the upper at 103.5 MPa. Data re-plotted from Yayanos et al. (1981).
	Figure 3. The growth rate of MT41 as a function of pressure at 275 K. Data re-plotted from Yayanos et al. (1981).
	Figure 4. The membrane fatty acids of bacterial isolate PE36 from cultures grown at three different pressures: 0.1 MPA (tan); 34.5 MPa (purple); and 62 MPa (green). The fatty acid composition changes as a function of pressure. Noteworthy is the occurrence of 22:6 fatty acids in this bacterium. Polyunsaturated fatty acids are widely distributed among deep-sea bacteria. Bar graph is based on data tabulated in DeLong and Yayanos (1986).

References
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	book Yayanos AA (2000) "ZoBell and his contributions to piezobiology (barobiology)". In: Bell CR, Brylinsky M and Johnson-Green P (eds) Microbial Biosystems: New Fronteirs. Proceedings of the 8th Eighth International Symposium on Microbial Ecology, pp. 689–694. Halifax, Canada: Atlantic Canada Society for Microbial Ecology.
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Further Reading
	Abe F (2007) Exploration of the effects of high hydrostatic pressure on microbial growth, physiology and survival: Perspectives from piezophysiology. Bioscience Biotechnology and Biochemistry 71(10): 2347–2357.
	Bartlett DH, Kato C and Horikoshi K (1995) High pressure influences on gene and protein expression. Research in Microbiology 146: 697–706.
	Deming JW (1986) Ecological strategies of barophilic bacteria in the deep ocean. Microbiological Sciences 3: 205–211.
	book Hamann SD (1957) Physico-chemical Effects of Pressure. London: Butterworths Scientific Publications. 246 pp.
	Jannasch HW and Taylor CD (1984) Deep-sea microbiology. Annual Review of Microbiology 38: 487–514.
	book Johnson FH, Eyring H and Polissar MJ (1954) The Kinetic Basis of Molecular Biology. New York: Wiley. 874 pp.
	Lauro FM and Bartlett DH (2008) Prokaryotic lifestyles in deep sea habitats. Extremophiles 12(1): 15–25.
	book Markley JL, Northrop DB and Royer CA (1996) High-Pressure Effects in Molecular Biophysics and Enzymology New York: Oxford University Press. xiv, 381 pp.
	book Yayanos AA (1998) "Empirical and theoretical aspects of life at high pressures in the deep sea". In: Horikoshi K and Grant WD (eds) Extremophiles, pp. 47–92. New York: Wiley.

Article Title:	Piezophiles
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