Haloferax volcanii

Ancient salt lover

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Haloferax volcanii occurs in the salt water of the Dead Sea. This archaea is a halophile: it grows in environments with a very high salt concentration. They are single-celled organisms of 1 to 3 micrometres in size that reproduce by binary fission: division into two identical cells.

Haloferax volcanii occurs in the salt water of the Dead Sea. This archaea is a halophile: it grows in environments with a very high salt concentration. They are single-celled organisms of 1 to 3 micrometres in size that reproduce by binary fission: division into two identical cells.

Practical pigments

The Dead Sea is often exposed to high levels of UV radiation. Haloferax volcanii has pigments that are located just below the cell wall that protect the interior of the cell against UV radiation. This species can have disc-shaped to cube-shaped cells.

Carotene sunscreen

The Dead Sea owes its name to the high salt concentration that makes life impossible for organisms such as fish and aquatic plants. The salt concentration is around 34%, ten times higher than in the ocean. Until 1936 it was thought that there was no life at all, until microbiologist Benjamin Volcani discovered that the Dead Sea actually does contain life, like this archaea.

In addition to protection against UV radiation, the pigments protect Haloferax volcanii also against other forms of stress. These brightly coloured pigments, called carotenoids, are also found in some bacteria and plants. Beta-carotene is perhaps the best known pigment, which gives carrots and pumpkins their colour. In stressful situations, such as high doses of UV radiation or changing salt concentrations, Haloferax volcanii also colours bright orange to red. If it rains heavily over the Dead Sea, and the salt concentration decreases sharply, the archaea can be noticed by a totally red sea.

Earthlings on mars?

Many archaea species have been discovered in extreme environments. High pressure, low pH, almost boiling water: so-called extremophiles grow there easily. Haloferax volcanii, compared to other extremophile organisms, is easy to grow in a laboratory. This is one of the reasons why astrobiologists are interested in this species. Astrobiologists are investigating, among other things, whether life is possible elsewhere than on Earth. The planet Mars has very salty, dry conditions with a high dose of UV radiation. In addition, there is practically no oxygen in the atmosphere of Mars, it consists of 96% carbon dioxide. These conditions are a piece of cake for Haloferax volcanii.

Unfortunately, not all problems of life on Mars have been overcome. The biggest problem is the average temperature of -63°C. In addition, it is not yet known how archaea deal with the 200 times lower pressure in the atmosphere of Mars. Who knows which circumstances so far undiscovered extremophiles can handle.