✿ 今日主題:深埋海底的微生物反映了陸地起源
Microbes Deep under Seafloor Reflect Ancient Land Origins

✿ 托福聽力最好的課外教材:60-Second Science

✿ MP3音檔:http://bit.ly/1PmkDhR

✿ 聽不懂地方,再來參考中英文稿:

Microbial organisms live in you, on you, in soil,in clouds and below the ocean floor. That last batch of single-celled critters is particularly hard to study. Not only are the samples difficult to obtain, but they can easily be contaminated with all that other microbial life once we dig them up.

So researchers had to take special precautions when they investigated microbial life in a coal bed deep below the seafloor near Japan. This material was once dry land, but got submerged some 20 million years ago.

The research team drilled nearly 2,500 meters below the seafloor and brought up samples. They carefully avoided contamination and evaluated only the inner portions of the samples, which were protected by the outer parts.

Analysis found life tenaciously holding on well under the ocean. A gram of rich garden soil can hold a billion bacteria—at 2,500 meters below the seafloor a gram of sediment might be home to just a single microbe. And those deeply buried organisms are quite different from microbes to be found just under the seafloor.

In that deep layer, the microbes are most closely related to bacterial groups that thrive in forest soils on land. The scientists thus suggest that the deeply buried undersea microbes might be descendants of ones that survived when their terrestrial habitat became flooded. Again, that was 20 million years ago. The finding is in the journal Science.

In a commentary in the same issue, Julie Huber of the Marine Biological Laboratory at Woods Hole says the fact that there's 「a massive buried biosphere」 has global importance 「with sub-seafloor microbes playing a crucial role in carbon sequestration…and Earth's evolution, and likely encompassing staggering metabolic and genetic diversity.」 She adds, 「We still have a long way to go in uncovering and understanding microbial life deep beneath the seafloor.」
在同期的一篇評論文章中,來自伍茲霍爾的海洋生物實驗室的朱莉‧胡貝爾(Julie Huber)稱大量被掩埋的生物圈對全球有著重要的作用。「海底下的微生物對碳封存...以及地球進化有著重要的作用,甚至可能對驚人的代謝能力以及遺傳 的多樣性也意義非凡。」她還補充說道:「我們離揭示和理解海底微生物的奧秘還有很長的距離。」


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