快猫短视频

A 鈥淟AZARUS鈥� bacterium which thrived millions of years before dinosaurs walked
the Earth has been brought back to life. Biologists are astonished that the
250-million-year-old bug could be revived, suggesting that if conditions are
right, bacterial spores might survive indefinitely.

It also adds weight to the controversial notion that life was scattered
throughout the cosmos by comets. The theory, put forward in 1981 by astronomer
Fred Hoyle, suggests that comets 鈥渟eeded鈥� life on Earth.

Provisionally named Bacillus permians to denote the geological
period from which it originates, the born-again bacterium is unknown to science.
鈥淚t is alive and, to the best of anyone鈥檚 knowledge, there鈥檚 no other organism
that鈥檚 been around that long,鈥� says Russell Vreeland, the scientist who isolated
the bacterium. Its nearest 鈥渁ncient鈥� rivals are bacterial babes by comparison,
just 25 to 40 million years old
(快猫短视频, 17 May 1997, p 7).

Vreeland and his colleagues at West Chester University in Pennsylvania
isolated the ancient bacterium from the Salado salt formation at Carlsbad, New
Mexico, an underground cavern used for storing nuclear waste. While the salt
crystals were forming 250 million years ago, bacterial spores in a drop of water
became trapped in a cavity in the salt鈥攁 feature known as an inclusion.
鈥淭he inclusion looks like a cube within a cube,鈥� says Vreeland. Geologists dated
the layer where the crystal was found鈥�560 metres down in a shaft leading
to the repository鈥攁t 250 million years old.

Under scrupulously sterile conditions, Vreeland liberated the spores from
their hibernation. He extracted the 3-microlitre inclusion and squirted it onto
growth medium. The spores grew into familiar rod-shaped bacillus bacteria. 鈥淚
think the cell wall is a little thicker than in normal bacillus bacteria,鈥� he
says. Vreeland is now comparing the genes of the ancient bug with those of two
contemporary relatives: Bacillus marismortui, from the Dead Sea, and
Virgibacillus pantothenticus.

John Parkes, a geomicrobiologist at the University of Bristol, says that
survival of such ancient spores is astonishing. 鈥淎ll the laws of chemistry tell
you that the complex molecules in the spores should have degraded to very simple
compounds such as carbon dioxide,鈥� he says.

Parkes says that before people start jumping to conclusions, they should wait
until someone else finds similar bacteria from the same salt formation. But if
it is proven that spores can survive this long, he wonders, why should they die
at all? 鈥淲here else are these dormant organisms waiting to be reawakened?鈥�