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The Most Extreme Environment: Time

Examining core samples of ancient salty sediments in Death Valley, scientists found micron-wide bubbles of water trapped in salt crystals that contained small communities of microbes. The organisms, several varieties of salt-loving, bacteria-like Archaea, had been trapped aliveófor 34,000 years.

Many bacteria will turn into spores when faced with extreme conditions; in this form, they may survive in a suspended state for a very long time. (A few years ago, someone reported viable sporulated bacteria from the Permian, some 250,000,000 years old; their results have not been reproduced, and it’s now believed that the bacteria they found were the result of contamination in the lab.) The salt-loving prokaryotes in Death Valley, which like bacteria lack nuclei or other specialized internal structures wrapped in membranes, don’t sporulate. Instead, they seemed to have taken on the constricted, “starvation” shape many of their cousins adopt in low-quality environments. It’s as if they had been hibernatingóalive but not moving or reproducingófor tens of millennia. And when removed from their haline prisons, some of the organisms began to reproduce.

They likely survived their lengthy interment thanks to another inmate of the salt crystals’ fluid inclusions: single-celled algae called Dunaliella, which produce glycerol and beta carotene. This is a slow ecosystem pared to its essentials: a producer and a consumer.

As we’ve learned with arsenic-tolerant bacteria and the shadow biosphere, understanding what’s going on with microbes in extreme environments is subtle, difficult work; these results might evaporate faster than a puddle in Death Valley. Questions abound: how do these organisms repair their DNA, which degrades over long time periods? What life functions were they able to carry out, and which could they safely turn off? But if this discovery (reported in a highly readable paper in GSA Today, the journal of the Geological Society of America) are confirmed, it’s a remarkable example of life surviving in the most extreme environment of all: time. óvia LiveScience

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