Adaptation to temperature

Unsaturations of lipids play a key role in lipid homeostasis, where organisms adapt to temperature variations of the environment. Plants and animals maintain physiological functions by reversibly altering the composition and conformation of lipid molecules of the cell membrane. To achieve this, they extensively and elegantly use the unsaturations (double bonds) present in their side chains. This is the process by which cell membranes adjust their flexibility (fluidity) of the bilayer and adapt themselves to perturbations in temperature, pressure, and other variations in the natural environment [11-14]. They remain indispensable for the poikilothermism exhibited by fishes, invertebrates, and amphibians [15, 16]. Commercially,... 

Walsh, P.J. (1981). Purification and characterisation of glutamate dehydrogenases from three species of sea anemones adaptation to temperature within and among species from different thermal environments. Marine Biology Letters 2,289-299. 

The dissociation of water into hydrogen (hydronium, H30+) and hydroxyl ions is temperature dependent. As temperature is increased, dissociation of water is enhanced, such that the pH and pOH of a solution fall with rising temperature. Because of the large number of biological processes that are affected by changes in pH, the temperature pH relationship is an important aspect of adaptation to temperature. 

Exploiting the Comparative Approach to Study Adaptation to Temperature... 

Lactate dehydrogenase a model enzyme for studying adaptation to temperature... 

Figure 7.3 illustrates values of /ceat for orthologs of A4-LDH from vertebrates adapted to temperatures between — 1.86°C (Antarctic notothenioid fishes) and approximately 37 42°C (mammal, birds, and a thermophilic reptile) (Fields and Somero, 1998). All kalt values... 

The joint evolution of proteins and the solution in which they occur is an issue within evolution that we treat at numerous junctures in this volume. The types of effects noted for enzymes of M. fervidus and paralogs of MDH show that joint evolution of proteins and solutes may be of broad importance in adaptation to temperature. Data such as these also have a practical lesson for us they show that the complexity of the intracellular milieu must be carefully evaluated when designing and interpreting experiments done in vitro. All partners in the evolutionary process must be considered if the nature of physiological adaptation is to be appreciated. This point brings us to one of the most striking differences exhibited by proteins under in-vitro versus in-vivo conditions the extent to which the primary structure of the protein is able to direct its folding into the... 

The earliest general model of adaptation to temperature in membrane lipids focused on the physical state ( static order or viscosity [= 1 / fluidity ]) of the bilayer. The finding that the physical state of membrane lipids from Escherichia coli cultured at different temperatures was similar at the different growth temperatures led to the homeoviscous adaptation hypothesis, which states that lipid composition is modified during thermal acclimation to facilitate retention of a relatively stable membrane physical state (Sinensky, 1974). At the outset of any discussion of homeoviscous adaptation, it is important to examine carefully what is meant by physical state (or the related terms static order, viscosity, and fluidity ). In such an analysis, one must also consider the physical methods that are used to make such measurements—and the limitations of these techniques. 

In summary, cholesterol appears to play an important role in modifying membranes, at least the plasma membranes of animal cells, in temperature-compensatory manners. The significance of cholesterol in adaptation to temperature by animals raises several interesting evolutionary questions. Do the many taxa that lack cholesterol employ other types of molecules to achieve the sorts of adaptations effected by cholesterol in animal cells In view of the requirement for molecular oxygen for the synthesis of cholesterol, did the earliest cells, which evolved in the near absence of molecular oxygen, develop oxygen-independent synthetic pathways for producing lipids with cholesterol-like effects ... 

Bennett, A.F., and R.E. Lenski (1993). Evolutionary adaptation to temperature. II. Thermal niches of... 

Hazel, J.R. (1990). Adaptation to temperature phospholipid synthesis in hepatocytes of rainbow trout. Am. J. Physiol. 258 (Regulatory Integrative Comp. Physiol. 27) R1495-R1501. 

Stillman, J.H., and G.N. Somero (1996). Adaptation to temperature stress and aerial exposure in congeneric species of intertidal porcelain crabs (genus Petrolisthes) correlation of physiology, biochemistry and morphology with vertical distribution. J. Exp. Biol., 199 1845-1855. 

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