Locked in ice for millions of years, Antarctic bacteria are thawing – and they're alive. So will a prehistoric plague be swimming in a sea near you? 

Antarctica's Dry Valleys are among the most desolate places on the planet. Here, no plants cling to the slopes, no small mammals scurry among the scree. The freeze-dried landscapes, with their rocks chiselled by the wind, seem utterly lifeless. When Captain Scott first chanced upon their craggy peaks and troughs in 1905, he labelled them the "valleys of the dead".

Now, a little more than a hundred years on from Scott's exhibition, US scientists have discovered that the icy landscapes may not be so barren after all. Microbiologists from New Jersey have chanced upon tiny frozen organisms that have remained alive for millions of years, embedded in some of the oldest ice on the planet.

Dr Kay Bidle of Rutgers University, who was part of the research team, extracted DNA and bacteria from ice found barely metres beneath the surface of a Dry Valleys glacier, and, remarkably, claims to have grown the bacteria in a lab. "This is by far the oldest ice in which we have found encased microbes, cultured them and formed a growth," he says.

The discovery of such ancient viable genetic material has far-reaching implications, not least the possibility that global warming could melt Antarctic ice to such an extent that an army of invidious pathogens will be released to wreak havoc on humans. But a more realistic outcome is that the experiment will aid our understanding of evolution, and how life could survive on other planets. Not bad for organisms that are eight million years old, originating four million years before humans first got up and strolled about on two legs. "The study is interesting because it extends understanding of the period of time over which organisms remain viable," adds Dr Bidle, who published his research earlier this month.

Braving the barren hills, where footsteps made 50 years ago can still be seen, the researchers took samples that ranged in age from 100,000 to eight million years. Drilling deep beneath the shifting surface of an ice floe, they dredged up frozen material that, when scrutinised under a microscope, left them stunned. Not only could they see microscopic bacteria that they could extract, but these enduring creatures were from the most ancient ice samples.

Once the bacteria were extracted and fed in a laboratory, they began to multiply. While the number of organisms found in the 100,000-year-old ice doubled in size every seven days, those from the eight million-year-old ice grew much more slowly. Dr Bidle says that the "young stuff grew really fast", but the older colony doubled in size only every two months, suggesting that over time, the bacteria's DNA , which controls its reproduction, had been damaged.

The researchers claim this is the result of cosmic radiation – highly charged energy particles that whizz in from space and bash apart genetic material. This radiation is strongest at the poles, where the Earth's protective magnetic field is at its weakest. Comparing the genetic "mashing up" of the two samples, the scientists were able to calculate a half life for the bacterial DNA (how long it takes for half the DNA present in a sample to fall apart). The figure they came up with was a whopping 1.1 million years.

The scientific community has heralded the discovery as "significant", but the team's conclusions might disappoint science-fiction buffs. There will be no global pandemic – or at least there shouldn't be. The scientists say that while extremely old bacteria will be released into the world's oceans as a result of global warming, it is not a "cause for concern". Dr Bidle says that marine bacteria and viruses are less harmful to human health than those found on land. "Clearly this melting has happened many times over the Earth's history," he says. "We didn't find any pathogens. What we found were organisms closely related to common environmental bacteria."

The experts are keen to point out that even if ancient pathogens were released, they would not be very good at making people ill. In order to be effective they would have had to evolve in tandem with their original "target" – impossible for organisms that have been cut off for millenia.

Whenever the ice caps melt they inject a huge amount of genetic material into the oceans. Bacteria can incorporate external DNA into their own genetic material – through a process known as "lateral transmission"– and if they are good genes they can help the bugs survive. If they are not, they won't. "[Lateral transmission] can be advantageous or it can be deleterious. This is one of main ways in which microbes get new data," Bidle says. "It's up to natural selection to sort that out." In other words, the thawing of Antarctic ice could fast-track the microbes' evolution.

Moving back a notch, Bidle et al have shed light on how life on Earth began – or at least undermined a popular theory. Some scientists suggest a comet carrying the raw material for life crashed into the planet millions of years ago. But Bidle's team claim that, as the DNA in the old ice samples degraded massively as a result of exposure to cosmic radiation, life on Earth is unlikely to have come from outside the Solar System. A comet carrying life from beyond our immediate planetary neighbours would take so long to reach us that all the genetic material on it would be sterilised.

Read the full article at: The Independent

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