Thriving in Environmental Extremes

The ability of many members of the Archaea to thrive in environmental conditions that we would find extreme is perhaps one of their most fascinating characteristics. There are genus like Halobacterium, which inhabit extremely salty environments, such as the Great Salt Lake in Utah and the Dead Sea in Israel. The salt concentration in these lakes is at least ten times that of seawater. Still other lakes, like Lake Magadi in Kenya, are not only extremely salty, but are also extremely alkaline, with pH values as high as 10 or 12. Archaea can be found even here, and their names reflect their habitat: Natronobacterium, Natronosomonas, and Natronococcus ("natro" means "salt"). The reddish-purple color sometimes seen in seawater-evaporating ponds, where solar salt is prepared, is the result of the growth of red-pigmented Archaea.

Extremes of temperature offer no challenge to certain members of the Archaea. A number of species, in fact, require temperatures over 80 °C in order to grow. Some live quite happily in the superheated outflow of geot-hermal power plants. Others thrive in the conditions of extreme acidity and temperature found in sulfur-rich, acidic hot springs like those in Yellowstone National Park, in the United States.

The high-salt density of the Dead Sea makes it difficult for humans to swim in its waters. Human bodies are much more buoyant in the Dead Sea waters than in fresh water. It is possible to lay back in the water—floating as if on an air mattress.

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