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Study: ancient microbes may revive as glaciers melt

Aug. 12, 2007
Courtesy Rutgers
and World Science staff

The DNA of an­cient mi­crobes, long fro­zen in glaciers, may re­turn to life as the ice melts, a study has con­clud­ed. 

Glaciers have been melt­ing rap­idly due to glob­al warm­ing, ac­cord­ing to sci­en­tists. An­cient mi­croor­gan­isms and their DNA have been locked in this ice. It was­n’t known be­fore now wheth­er these could be re­vived, said Kay Bidle of Rut­gers, The State Un­ivers­ity of New Jer­sey, in New Bruns­wick, N.J. Bidle is lead au­thor of a pa­per on the find­ings to ap­pear in the Aug. 14 is­sue of the re­search jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces.

The Nim­rod Glac­i­er in Ant­arc­ti­ca. (Cour­te­sy NSF/USAP, Josh Lan­dis) 

Bidle and col­leagues melted five sam­ples of ice rang­ing in age from 100,000 to 8 mil­lion years old to find the mi­croor­gan­isms trapped in­sid­e. They wanted to know how long cells could stay vi­a­ble and how in­tact their DNA was. 

“First, we asked, do we de­tect mi­croor­gan­isms at al­l?” Bidle said. “We did – more in the young ice than in the old.” The young ones were easily grown and cul­ti­vat­ed in col­o­nies whose popula­t­ions “dou­bled eve­ry cou­ple of days.” Mi­crobes from the old­est ice dou­bled only eve­ry 70 days, and had signs of de­te­riora­t­ion in their DNA, he added.

DNA qual­ity showed a steep drop past about 1.1 mil­lion years, mak­ing it un­likely that bac­te­ria much old­er could sur­vive, he added.

The re­search­ers stud­ied Ant­arc­tic glaciers be­cause the po­lar re­gions con­tain Earth’s old­est ice and are sub­ject to more radia­t­ion from space than the rest of the plan­et. It’s this radia­t­ion “that’s blast­ing the DNA in­to pieces over ge­o­log­ic time, and most of the or­gan­isms can’t re­pair that dam­age,” Bidle said.

Be­cause the DNA had de­ter­i­o­rated so much in the old ice, the re­search­ers al­so con­clud­ed that life on Earth, how­ev­er it arose, did not ride in on a com­et or oth­er de­bris from out­side the so­lar sys­tem, as a pop­u­lar the­o­ry called pan­sper­mia holds. Cos­mic radia­t­ion would have killed such life, they said.

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The DNA of ancient microbes, long frozen in glaciers, may return to life as the ice melts, a study has concluded. Glaciers have been melting rapidly due to global warming, according to scientists. Ancient microorganisms and their DNA have been locked in this ice. It wasn’t known before now whether these could be revived, said Kay Bidle of Rutgers, The State University of New Jersey, in New Brunswick, N.J. Bidle is lead author of a paper on the findings to appear in the Aug. 14 issue of the research journal pnas. Bidle and colleagues melted five samples of ice ranging in age from 100,000 to 8 million years old to find the microorganisms trapped inside.They wanted to know how long cells could stay viable and how intact their DNA was. “First, we asked, do we detect microorganisms at all?” Bidle said. “We did – more in the young ice than in the old.” The young ones were easily grown and cultivated in colonies whose populations “doubled every couple of days.” Microbes from the oldest ice doubled only every 70 days, and had signs of deterioration in their DNA, he added. DNA quality showed a steep drop past about 1.1 million years, making it unlikely that bacteria much older could survive, he added. The researchers studied Antarctic glaciers because the polar regions contain Earth’s oldest ice and are subject to more radiation from space than the rest of the planet. It’s this radiation “that’s blasting the DNA into pieces over geologic time, and most of the organisms can’t repair that damage,” Bidle said. Because the DNA had deteriorated so much in the old ice, the researchers also concluded that life on Earth, however it arose, did not ride in on a comet or other debris from outside the solar system, as a popular theory called panspermia holds. Cosmic radiation would have killed such life, they said.