Preservation of Miocene glacier ice in East Antarctica

Sugden, David E.; Marchant, David R.; Potter, Noel; Souchez, Roland; Denton, George H.; Swisher, Carl C.; Tison, Jean-Louis

doi:10.1038/376412a0

Cited by 235 publications

(228 citation statements)

References 18 publications

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“…‡ Four-kilobase amplification results were replicated on a duplicate sample of permafrost 500K in the Ancient DNA Research Laboratory, Murdoch University. § Sample 1M was taken from beneath an 8.1-Ma volcanic ash layer that has been interpreted as a direct air-fall deposit (27). The antiquity of Sample 1M is supported by a number of studies (28 -30).…”

Section: Resultsmentioning

confidence: 93%

Ancient bacteria show evidence of DNA repair

Johnson

Hebsgaard²,

Christensen³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

265

178

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Recent claims of cultivable ancient bacteria within sealed environments highlight our limited understanding of the mechanisms behind long-term cell survival. It remains unclear how dormancy, a favored explanation for extended cellular persistence, can cope with spontaneous genomic decay over geological timescales. There has been no direct evidence in ancient microbes for the most likely mechanism, active DNA repair, or for the metabolic activity necessary to sustain it. In this paper, we couple PCR and enzymatic treatment of DNA with direct respiration measurements to investigate long-term survival of bacteria sealed in frozen conditions for up to one million years. Our results show evidence of bacterial survival in samples up to half a million years in age, making this the oldest independently authenticated DNA to date obtained from viable cells. Additionally, we find strong evidence that this long-term survival is closely tied to cellular metabolic activity and DNA repair that over time proves to be superior to dormancy as a mechanism in sustaining bacteria viability.

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Section: Resultsmentioning

confidence: 93%

Ancient bacteria show evidence of DNA repair

Johnson

Hebsgaard²,

Christensen³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

265

178

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“…1 A). These ice chronologies are supported by 3 He and 21 Ne cosmogenic dating of surface boulders (5) and laser-fusion 40 Ar/ 39 Ar radiometric dating of surface ash-fall deposits (6,7) [supporting information (SI) Text]. Analyses of the ice crystal structure and stable-isotope composition (␦ 18 O, ␦D) indicate that the ice samples have remained frozen since transformation from snow to glacier ice (e.g., refs.…”

mentioning

confidence: 76%

Fossil genes and microbes in the oldest ice on Earth

Bidle

Lee

Marchant

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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138

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Although the vast majority of ice that formed on the Antarctic continent over the past 34 million years has been lost to the oceans, pockets of ancient ice persist in the Dry Valleys of the Transantarctic Mountains. Here we report on the potential metabolic activity of microbes and the state of community DNA in ice derived from Mullins and upper Beacon Valleys. The minimum age of the former is 100 ka, whereas that of the latter is Ϸ8 Ma, making it the oldest known ice on Earth. In both samples, radiolabeled substrates were incorporated into macromolecules, and microbes grew in nutrient-enriched meltwaters, but metabolic activity and cell viability were critically compromised with age. Although a 16S rDNA-based community reconstruction suggested relatively low bacterial sequence diversity in both ice samples, metagenomic analyses of community DNA revealed many diverse orthologs to extant metabolic genes. Analyses of five ice samples, spanning the last 8 million years in this region, demonstrated an exponential decline in the average community DNA size with a half-life of Ϸ1.1 million years, thereby constraining the geological preservation of microbes in icy environments and the possible exchange of genetic material to the oceans.ancient ice ͉ community DNA ͉ metabolism ͉ metagenomic analysis ͉ cosmic radiation A ntarctica offers unique environments for understanding the limits of biological metabolism and geological preservation of life and genetic material. Analyses of microorganisms in subglacial lakes, including Lake Vostok (1) and Lake Bonney (2), as well as the Taylor Dome region of the Transantarctic Mountains (3), have revealed the potential viability of microorganisms preserved in ice up to Ϸ300 ka. In the Dry Valleys of the Transantarctic Mountains, however, patches of much older ice persist, yet little is known about the viability of microbes or the state of genetic material in these regions.Here we report on the microbial activity and state of the community DNA in samples from a debris-covered alpine glacier that heads in Mullins Valley (sample no. DLE-98-12) and terminates along a diffuse boundary in Beacon Valley (sample no. EME-98-03) ( Fig. 1 A and B). Synthetic aperture-radar interferometry analysis indicated that ice within Mullins Valley ranges from modern at the valley head to Ϸ300 ka near the tributary mouth, whereas buried ice on the floor of upper and central Beacon Valley could be as much as 10 Ma (4). DLE-98-12, which is assigned an age of Ϸ100 ka, lies halfway down Mullins Valley, whereas EME-98-03 lies in the zone estimated to be up to 8 Ma (Fig. 1 A). These ice chronologies are supported by 3 He and 21 Ne cosmogenic dating of surface boulders (5) and laser-fusion 40 Ar/ 39 Ar radiometric dating of surface ash-fall deposits (6, 7) [supporting information (SI) Text]. Analyses of the ice crystal structure and stable-isotope composition (␦ 18 O, ␦D) indicate that the ice samples have remained frozen since transformation from snow to glacier ice (e.g., refs. 6 and 7). There were also no dete...

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“…Examples of where the preservation of buried-ice has been permitted on longer timescales include formerly glaciated continental settings (e.g. Ingólfsson and Lokrantz, 2003;Murton et al, 2005), and cold deserts where buried-ice is suggested to have existed for several millennia under permafrost conditions (Sugden et al, 1995;Schäfer et al 2000). Waller et al (2012) highlighted that the preservation of buried-ice may be permitted on geological timescales if it is located at depths unaffected by seasonal thaw.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%