Extremophilic organisms

Even extremophilic organisms and their proteins contain the same 20 amino acids with bonds similar to those in mesophiles. As the difference in free enthalpy between folded and unfolded states of globular proteins AG N >G is only about 45 15 kj mol-1 the sequence and structure of extremophilic proteins should differ from those of ordinary species. However, the main question, namely which properties cause the increase in denaturation temperature of thermostable proteins, is still debated (Rehaber, 1992). Theoretical and experimental analyses have shown that thermal stability is largely achieved by small but relevant changes at different locations in the structure involving electrostatic interactions and hydro-phobic effects (Karshikoff, 2001). There is no evidence for a common determinant or for just one effect causing thermostability. 

Fig. 1. Optimal growth temperatures for mesophilic and extremophilic organisms.

Proteins from extremophilic organisms, particularly thermophiles, have been the subject of intensive research in recent years. This work has been the subject of numerous reviews (Jaenicke and Bohm, 1998 Russel and Taylor, 1995 Vogt and Argos, 1997 Gerday et al., 1997 Somero, 1995), and we will make no attempt at an in-depth summary. We will confine ourselves to briefly stating the major trends identified thus far. Explaining these trends becomes complicated because the many weak interactions that determine enzyme stability and activity have complex temperature dependencies (see Section II). And evolution injects considerable confusion beyond the laws of physical chemistry. 

Abstract The strategic adaptation of extremophiles (organisms which can survive where humans... 

The stability of all these organisms is essentially determined by the stability of the proteins and conjugated proteins occurring in them. Proteins in extremophilic organisms generally do not differ from those in mesophilic organisms with respect to the primary, secondary, and tertiary structure. But... 

Extremophile an organism that is isolated from an extreme environment and often requires the extreme condition for growth. 

The structural integrity of enzymes in aqueous solution is often compromised by the addition of small quantities of water-miscible organic solvents. However, there are numerous examples, particularly using extremophiles, where enzymes have been successfully employed in organic solvent-aqueous mixtures.A good example is the savinase-catalysed kinetic resolution of an activated racemic lactam precursor to abacavir in 1 1 THF/water (Scheme 1.39). The organic solvent is beneficial as it retards the rate of the unselective background hydrolysis. 

Butler, L.G., Enzymes in non-aqueous solvents. Enzyme Microb. Technol., 1979,1, 253-259. Gerard A. Sellek, G.A. and Chaudhuri, J.B., Biocatalysis in organic media using enzymes from extremophiles. Enzyme Microb. Technol., 1999, 25, 471-482. 

Recently, organic solvent tolerant bacteria, a novel group of extremophilic microorganisms that combat these destructive effects and thrive in the presence of high concentrations of organic solvents as a result of various adaptations, are being explored for their potential in industrial and environmental biotechnology [29],... 

A very interesting research area in biology and biotechnology is the topic of extremophiles. Life on Earth has adapted over the course of evolution, even to extreme habitats (although there is evidence that organisms had to adapt to ever cooler conditions on Earth over the course of early evolution). Extreme habitats encompass the range of conditions as described ... 

Enzymes from extremophiles, such as thermozymes, have potential either as products themselves, or as catalysts, or they may be used as sources of ideas to modify mesophile-derived enzymes. Most of the thermozymes maintain their thermoresistant properties when expressed in a mesophilic organism such as... 

Escherichia coli (Niehaus, 1999). Whereas halophiles (Margesin, 2001) and piezo-philes (Abe, 2001) have attracted attention, the main aspect of interest for biotechnological application remains thermal stability, focusing interest on thermophiles or even hyperthermophiles. Increase in temperature has a significant influence on the bioavailability and solubility of organic compounds (not on the solubility of Oz, however, which is nearly zero at extremophilic temperatures ). Current applications of extremozymes include ... 

The examples cited above illustrate that there are currently several alternatives to bulk harvest for the supply of bioactive marine natural products and several more in development. However, as the ability to access organisms in more extreme environments improves, conditions required for growth of these extremophiles will be more complex and difficult to reproduce. 

---