英語聽力文摘 地球上最成功的物種

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地球上最成功的物種

For many scientists, a species’ success is measured by sheer numbers. In that case, the most successful species known to man is a type of bacterium known as S-A-R-11, or SAR-11 for short. Scientists estimate that there are two-hundred and forty times a billion billion billion SAR11 cells floating around in the oceans. Now that makes six-billion humans sound like a mere handful.

SAR11 bacteria are known for their ability to transform one substance into another, which is why they are such an important part of the Earth’s chemical cycles. Although scientists are still uncertain about SAR11′s specific role, it appears to produce carbon dioxide using the oxygen and carbon from organic matter that’s derived from photosynthesis. Scientists speculate that SAR11 plays a major role in the way the ocean’s surface acts as a giant carbon pump that removes carbon dioxide from the atmosphere.

The catch is that SAR11 is what is known as an uncultured organism, which means that scientists haven’t been able to cultivate it under laboratory conditions. This requires scientists to develop pretty indirect genetic methods just to be able to study SAR11 cultures. Now that this technology is available, scientists are sequencing the SAR11 genome in order to figure out exactly what kinds of carbon it uses, and why it’s so successful at ocean living.

對很多科學(xué)家來說，一個(gè)物種的成功完全取決于數(shù)量。如果是那樣是話，為人類所知的最成功的物種就是一種簡稱“SAR-11”的細(xì)菌?？茖W(xué)家們估計(jì)海洋中的SAR11細(xì)胞的數(shù)量超過2 x 10的28次方個(gè)。那讓60億人類聽起來屈指可數(shù)。

SAR11細(xì)菌以其轉(zhuǎn)換物質(zhì)的能力為人所知。而這也使得它們成為地球化學(xué)循環(huán)中重要的部分。盡管科學(xué)家不能確定SAR11的具體作用。但它似乎可以使來自于光合作用的氧氣和有機(jī)物種的碳發(fā)生作用，產(chǎn)生二氧化碳。科學(xué)家推測SAR11在海洋表面扮演著重要的作用，作為一個(gè)巨大的碳泵移除空氣中的二氧化碳。

但目前SAR11是為培養(yǎng)生物，也就是說科學(xué)家不能在實(shí)驗(yàn)室里培養(yǎng)出這種細(xì)菌。因此需要科學(xué)家們研制出間接遺傳方法，來研究SAR11。既然這項(xiàng)技術(shù)可用，科學(xué)家為了弄清楚究竟SAR11用的是哪種碳以及為什么它會如此的成功在海洋中生活，正在排序它的基因組。