Extreme Thermophiles

Abstract

Abstract Extreme thermophiles are microorganisms adapted to temperatures normally found only in hot springs, hydrothermal vents and similar sites of geothermal activity. These microorganisms include diverse archaea and bacteria and represent a wide range of metabolic strategies. The geothermal environments populated by extreme thermophiles provide chemical resources for microbial metabolism. Various molecular features enable the cells of extreme thermophiles to function optimally at these temperatures, which kill other cells. These features include low‐molecular weight compounds that stabilise the conformations of proteins and nucleic acids, enzymes with intrinsically stable folded conformations and unusual lipids that form highly impermeable membranes. Metabolic activities and intrinsically stable enzymes of extreme thermophiles offer advantages for industrial and diagnostic processes ranging from ore processing to molecular genotyping. Key Concepts Bacteria and archaea consist of very simple (prokaryotic) cells but they vary greatly with respect to metabolic capabilities, physiological limits and other fundamental properties. The term ‘extreme thermophile’ usually denotes a microorganism which requires the temperatures found in geothermal environments for its optimal growth. Geothermal environments provide inorganic nutrients and sources of chemical energy that certain bacteria and archaea can utilise. Extreme thermophiles use two general strategies to avoid thermal denaturation of their enzymes: extrinsic stabilisation, conferred by certain small molecules, and intrinsic stabilisation, conferred by the specific structure and conformation of the enzyme itself. The intrinsically thermostable enzymes of extreme thermophiles are useful for biotechnology because they allow chemical reactions to be catalysed with high specificity at high temperatures or under other harsh conditions.