Extremophile mesophilic

Proteins, independent of their mesophilic or extremophilic origin, consist exclusively of the 20 canonical natural amino acids. It is therefore interesting to understand the reasons how some proteins are stabilized so as to resist exceptional temperatures. 

Cannio, R. Contursi, P. Rossi, M. Bartolucci, S. Thermoadaptation of a mesophilic hygromycin B phosphotransferase by directed evolution in hy-perthermophilic Archaea selection of a stable genetic marker for DNA transfer into Sulfolobus solfataricus. Extremophiles, 5, 153-159 (2001)... 

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. 

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... 

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

It is revealing to contrast the adaptations noted in proteins and in lipids among the hyperthermophiles. Proteins of these extremophiles look surprisingly similar to those of mesophiles and psychrophiles. Proteins, as... 

Mounting so cial, p olitical a nd e nvironmental p ressures on i ndustry t o provide alternatives to chemical-based methods, have given added impetus to the search for novel enzymes with unique and industrially significant traits. Thus, numerous organisms have been isolated from extreme environments. From the frosty A ntarctic ice fields to t he fiery v olcanic p ools, these o rganisms p ossess unique survival kits that allow them to survive under these extreme conditions. In most cases, adaptation to such extreme environments has not required completely new molecular machinery in fact many "extremophilic enzymes are similar to dieir mesophilic counterparts found in more hospitable environment. Sequence comparisons indicate that these enzymes are derived from a common... 

For most forms of life, physiological conditions correspond to temperatures of about 25 C, atmospheric pressures of about 1 bar, and osmotic pressures of about 5 bar. Such organisms are called mesophillic. Besides these, there are also extremophilic forms of life which can only exist under extreme conditions. What are known as thermophilic organisms can occur in hot springs, deserts, and compost heaps and these can withstand... 

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... 

Most of the enzymes used to date are obtained from mesophilic organisms and, thus, their limited stability to temperature, pH, or ionic strength. Ex-tremophiles are organisms that have evolved to exist in a variety of extreme environments. Table 3 lists the range of habitats where extremophiles have been found and some of the identified extremozymes. Adaptation to extreme conditions means that these enzymes have the same order of magnitude of activity and stability but at different temperatures, ionic... 

There are many existing and potential industrial applications of extremophilic enzymes (see Table 2), which take advantage of their capacity to thrive in harsh conditions, relative to their mesophilic (ie, function under moderate conditions) counterparts. For example, the detergent industry makes extensive use of alkaline-stable proteases, accounting for approximately 30% of global enzyme production (27). Enzymes from extremophiles have been used for bioremediation heavy metals and radionuclides from wastewaters (28), as well as for biodegrading hydrocarbons in polar soils (29). It is likely that extremophilic enzymes will find wide use in applications that strategically use their intrinsic robustness as biocatalysts. 

Extremophiles. Site ofthe scientific journal published by Springer from which one can download all the articles published in pdf format. See also http //library.thinkquest.org/CR0212089/home.htm This website contains many information on Acidophiles, Alkaliphiles, Barophiles, Halophiles, Mesophiles, Psychrophiles Thermophiles and Xerophiles. 

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