Adaptation to low temperature

A shift in temperature from 38 to 22 °C leads to desaturation of fatty acids in Anabaena variabilis [110], resulting in control of the fluidity of the plasma membrane. Mutants have been isolated in Synechocystis PCC 6803 that were defective in desaturation of fatty acids, and the growth rate of one of these mutants was much lower than that of the wild-type at 22 °C [112]. It turned out that the mutant strain had a mutation in the gene desA, and when the wild-type allele was introduced into the chilling-sensitive cyanobacterium Anacystis nidulans, it resulted in increasing the tolerance of that strain to low temperature [113]. These experiments nicely demonstrate the existence of a mechanism of adaptation to low temperature in a chilling-tolerant cyanobacterium. 

It has been generally accepted that the thermal decomposition of paraffinic hydrocarbons proceeds via a free radical chain mechanism [2], In order to explain the different product distributions obtained in terms of experimental conditions (temperature, pressure), two mechanisms were proposed. The first one was by Kossiakoff and Rice [3], This R-K model comes from the studies of low molecular weight alkanes at high temperature (> 600 °C) and atmospheric pressure. In these conditions, the unimolecular reactions are favoured. The alkyl radicals undergo successive decomposition by [3-scission, the main primary products are methane, ethane and 1-alkenes [4], The second one was proposed by Fabuss, Smith and Satterfield [5]. It is adapted to low temperature (< 450 °C) but high pressure (> 100 bar). In this case, the bimolecular reactions are favoured (radical addition, hydrogen abstraction). Thus, an equimolar distribution ofn-alkanes and 1-alkenes is obtained. 

Organisms Adapted to Low Temperature, Univ. Massachusetts Marine Station, Gloucester, 1978. 

We had to choose one of the earliest and least precise of the numerous methods for viscosity measurements that have been developed over the years, because the falling-sphere method was the only one that could be adapted to low-temperature measurements. The determination of viscosity was made by measuring the resistance to motion of a falling sphere in the fluid. Since the viscosities measured in our experiments on aqueous-organic mixtures at cryogenic tern-... 

The first type of device is used to cool relatively small sample volumes (a few milliliters). It is especially well adapted to low-temperature spectrophotometry. The liquid cooler is mainly used to cool large volumes (liters). In this case, although temperature variations are possible, they are slow because of the thermal inertia of the system. 

Small (1-5 g) scale UV photolysis of air sensitive compounds can be performed in quartz Schlenk tubes, or in conventional Schlenkware with the use of a UV transparent quartz stopper. The latter apparatus is easily adapted to low temperature irradiations. Large scale (10-50 g) UV photochemical reactions use quartz immersion well reactors. Medium pressure Hg-arc lamps are the preferred radiation sources for synthetic applications. ... 

Klein, W., Weber, M.H. and Marahiel, M.A. Cold shock response of Bacillus subtilis isoleucine-dependent switch in the fatty acid branching pattern for membrane adaptation to low temperatures. JBacterial, 181 (1999) 5341-5349. 

They appear to grow relatively slowly which may be an adaptation to low temperature and low nutrient availability rather than a direct effect of high pressure. The degradation of organic material appears to be just as efficient in the deep sea as in shallower water, since only a few percent of sedimenting detritus resist mineralization and are buried deep down into the sediment. 

What are some of the ways heat maintenance is more efficient for humans adapted to low temperatures compared to humans adapted to high temperatures ... 

Previously Potvin has examined C4 cold tolerance of ecotypes ofEchinochloa crus-gal 1i, cotrasting climates and shown biochemical and physiological adaptations to low temperature in the more northerly populations, (3,4,5). However, this work did not consider photoinhibition. This present study shows that greater tolerance to photoinhibition exists in some ecotypes may be a further factor involved in allowing cold tolerance. 

The cold-grown plants showed an increased qQ at low temperature, compared with control plants. This can be interpreted as an increased ability to perform linear electron transport at low temperature and as an adaptation to low temperature, diminishing the danger of photoinhibition. At 19°C measuring temperature, this relative increase... 

Fig. 7.1 Unsaturated fatty acids introduce kinks into phospholipids that are one mechanism by which cell membranes can adapt to low temperatures and high pressures by increasing membrane fluidity, (a) Depiction of the structure of a phospholipid containing saturated lipids, (b) Introduction of a single double bond creates a kink in the lipids, (c) Overall effect on the membrane structure of (a) and (b). Unsaturated phospholipids make the membrane less well-stacked (more fluid)...

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