Halophilous

A halophilous organization (of the Greek alos , salt and philein , to like) is an organization which has an absolute need for strong salt concentrations to live. The halophilous organizations are Extrémophile S pertaining to the fields of the Archaea or Bactérie S.

The halophilous organizations are isolated from lakes and salted ponds, of saline Marais, marine sediments. They can be met in the Big lake Salted in Utah, the Lac Owens in California, the Dead Sea, the estuaries of the Baie of San Francisco, the Lac Magadi with the Kenya, the Lagune of Venice in Italy.

Among the halophilous examples of Archaea, the order of the Halobacteriale S coomprend the kinds Halobacterium , Halococcus , Haloarcula , Haloferax , Natronococcus .

One distinguishes two types of halophilies:
There is the simple halophilie or Halotolérance ;
and the strict halophilie or halophilie obligatory : The micro-organism is unable to cultivate in medium which is not hypersalin.

For example, the experiments of laboratory show that the halophilous Bactérie S develop in an optimal way in culture media containing 4 moles per liter of NaCl. In less than one mole per liter, the halophilous bacteria die.

These organizations accumulate within their Cytoplasme of important quantities of salt, primarily of the KCl, close to the Saturation. In this way, they prevent the water loss. However, these organizations subject a new cellular stress then: the saline stress, which should cause the insolubility and the precipitation of its proteins. In fact, in the halophilous organizations, the proteins not only are soluble and functional in strong concentrations in KCl, but they are denatured when the salt concentration decreases.

Currently, it is not possible to say with certainty if the halophilous proteins are the result of an adaptation to an extreme environment, or if on the contrary they represent the survival of living conditions primitive with strong content salt.

See too

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