Psychrophilous

A psychrophilous (of the Greek psukhros , cold) or cryophile is a type of organization adapted and able to survive cold temperatures. Representatives of the majority of the Taxon S of alive are able to live in environments with temperatures right in lower part of 0°C. But in general, one speaks about psychrophilous organizations for the micro-organisms (Bactérie S and Archaea).

Psychrophilous bacteria and Archaea

Classically, these organizations have an optimum of growth around 15°C with a maximum temperature of growth close to 20°C, but they can still live and multiply with 0°C. They are found in environments like sea water of the oceans Arctique or the Antarctic, in frozen grounds for example.

Members of the kind Pseudomonas , of the family of the Flavobacteraceae , some Bacillus , some Clostridium , Psychrobacter , Arthrobacter are psychrophilous examples of bacteria.

There exist psychrophilous Algue S which can develop in the ice of the glaciers, or on the surface of snow, in the polar regions or the mountains. The orsqu' they develop massively, they can give a red or green coloring to the surface of snow, like the alga of snow, Chlamydomonas nivalis .

The psychrophilous micro-organisms have physiological and ecological adaptations to the cold environments. The fluidity of the membranes decreases with the reduction in the temperature. In answer to that, the organizations increase the ratio of fatty-acid saturated on unsaturated fatty-acid in the lipidic membranes. The cells are protected from the formation from ice and the thaw. The Protein S and Enzyme S are adapted cold. Operation on the molecular level of proteins and psychrophilous enzymes is very studied in order to better include/understand the cold adaptation and for biotechnological applications possible.

The organizations Psychrotrophe S are micro-organisms having a good resistance cold and being able to grow at temperatures ranging between 0 and 40 °C. They have an importance in Microbiologie food because they can multiply in cooled environments and cause deteriorations of food or human pathology following the consumption of this contaminated food ( Aeromonas , Pseudomonas , certain species of the family of the Enterobacteriaceae , Listeria for example).

Other animals

Fish thrive in water frozen of the Antarctic Ocean and near the continental Slope of the the Antarctic. These fish are adapted to this type of extreme environment. For example, the species of the family of the Nototheniidae secrete proteins antifreeze and have enzymatic activities more effective than those of other fish. The Channichthyidés when with them, do not have a Hémoglobine in their sang.
The worm of glacier Mesenchytraeus solifugus can tolerate a temperature until -7°C without freezing.

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