Fossil genes and microbes in the oldest ice on Earth
Fossil genes and microbes in the oldest ice on Earth
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DOI：
10.1073/pnas.0702196104
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发表时间：
2007-08-14
影响因子：
11.1
通讯作者：
Falkowski, Paul G.
中科院分区：
文献类型：
--
作者：
Bidle, Kay D.;Lee, SangHoon;Falkowski, Paul G.
尽管过去3400万年在南极大陆形成的绝大多数冰已经消失到海洋中，但在横跨南极山脉的干燥山谷中，古老的冰块仍然存在。在这里，我们报告了来自Mullins和上游Beacon Vallees的冰中微生物的潜在代谢活动和群落DNA的状态。前者的最小年龄为100ka，而后者的最小年龄约为8 Ma，是地球上已知的最古老的冰。在这两个样本中，放射性标记的底物被结合到大分子中，微生物在营养丰富的融化水中生长，但代谢活动和细胞活力随着年龄的增长而严重受损。虽然基于16S rDNA的群落重建表明，两个冰样中的细菌序列多样性相对较低，但群落DNA的元基因组分析显示，现有代谢基因存在许多不同的同源基因。对该区域过去800万年的五个冰样的分析表明，群落DNA的平均大小呈指数下降，半衰期约为110万年，从而限制了冰冻环境中微生物的地质保存和遗传物质向海洋的可能交换。
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 approximate to 8 Ma, making it the oldest known ice on Earth. In both samples, radiolabeled substrates were incorporated into macromolecules, and microbes grew in nutrient-enriched melt-waters, 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 approximate to 1.1 million years, thereby constraining the geological preservation of microbes in icy environments and the possible exchange of genetic material to the oceans.