Earth's warming climate may bring germs frozen for millions of years in glaciers back to life, potentially increasing the speed of the evolution of microbes, recent research reveals.
Antarctica's Dry Valley of the Transantarctic Mountains are home to the oldest known ice on Earth. Researchers melted five block of ice cut from glaciers there to find entombed microbes 100,000 to 8 million years old.
To avoid contamination of the ice with modern germs that would confuse results, the scientists took elaborate precautions, soaking the blocks in ethanol as an antiseptic and melting away the outer inches of ice using sterile water to decontaminate them.
The researchers discovered microbes in all the ice, more in the young than in the old. They also grew them out in the lab.
"The young stuff grew really fast," said Rutgers University marine microbiologist Kay Bidle, doubling in number "every couple of days." Until now, scientists didn't know whether such ancient, frozen life could be revived, he added.
The older samples, on the other hand, grew very slowly, doubling only every 70 days. Genetic analysis revealed their DNA had in fact deteriorated significantly, probably because of cosmic radiation blasting it to pieces over time.
"There is still DNA left after 1.1 million years," Bidle said. "But 1.1 million years is the 'half-life' — that is, every 1.1 million years, the DNA gets chopped in half." He explained the average size of DNA in the old ice was 210 base pairs — that is, 210 units strung together. The average genome size of a bacterium, by comparison, is 3 million base pairs.
Ancient organisms might not survive such a long deep-freeze, but pieces of their DNA could. This suggests that as global warming melts the ice, these ancient genes could flow into the seas, which living microbes could suck up and use "to improve themselves, potentially altering their communities significantly," Bidle said.
Source:Xinhua/agencies
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