Salt Survivors

Joe Zaccai looks at new research on the substances that enable halophile bacteria to function in high salt concentrations

The Biologist 64(2) p24-27

Extremophile microorganisms, which thrive in physically or geochemically extreme conditions, arguably represent the most numerous forms of life on Earth.

They are present in diverse genetic lineages of bacteria and archaea that range all around the globe in particular environmental niches, including hot springs and around deep-sea hydrothermal vents where the water is very hot (thermophiles and hyperthermophiles); in saline ponds and salt lakes such as the Dead Sea (halophiles); in marine and salt marsh environments, where salt concentrations fluctuate over a broad range (halotolerant bacteria and archaea); in highly alkaline and acidic pools (alkaliphiles and acidophiles); and even inside hot rocks deep under the Earth's surface.

An organism found at the summit of a mountain in the Atacama Desert in South America is both a xerophile and psychrophile – thriving in low water availabilities and at cold temperatures.

The physical chemistry of extreme environments poses a serious challenge to biochemistry. In halophiles, how on Earth does DNA-protein recognition take place in molar salt concentrations?

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