科學60秒:彼之砒霜 吾之蜜糖
來源：滬江聽寫酷
2011-06-20 10:00
只寫5個空即可，最后一個空和第一個空的詞一樣，不用單寫出來。
Life on Earth requires six basic ingredients—carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus. Those six elements are the ____1____ for DNA and RNA, along with proteins and fats. Which means they're essential for life—as we know it. But it might be time to update that list. Because scientists have found a bacterium that can do without phosphorus—live on arsenic instead.
The researchers had a ____2____ a bug like this might exist, because arsenic has some ____3____ in common with phosphorus. So they collected mud from California's Mono Lake, where the waters are naturally salty, and laced with arsenic. Back in the lab, they cultured microbes from that mud. But instead of adding phosphorus to the cultures to help the bugs grow, they added varying levels of arsenic.
One bacterial ____4____ continued to thrive. And tests confirmed that the organisms ____5____ the lack of phosphorus by building their DNA with arsenic instead. The research appears in the journal Science.
This is the first known life form that seems to be able to swap out one of life's fundamental ____1____ with another element. So for astrobiologists hunting for life in space, don’t rule out places filled with poison.
【視聽版科學小組榮譽出品】
Life on Earth requires six basic ingredients—carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus. Those six elements are the ____1____ for DNA and RNA, along with proteins and fats. Which means they're essential for life—as we know it. But it might be time to update that list. Because scientists have found a bacterium that can do without phosphorus—live on arsenic instead.
The researchers had a ____2____ a bug like this might exist, because arsenic has some ____3____ in common with phosphorus. So they collected mud from California's Mono Lake, where the waters are naturally salty, and laced with arsenic. Back in the lab, they cultured microbes from that mud. But instead of adding phosphorus to the cultures to help the bugs grow, they added varying levels of arsenic.
One bacterial ____4____ continued to thrive. And tests confirmed that the organisms ____5____ the lack of phosphorus by building their DNA with arsenic instead. The research appears in the journal Science.
This is the first known life form that seems to be able to swap out one of life's fundamental ____1____ with another element. So for astrobiologists hunting for life in space, don’t rule out places filled with poison.
【視聽版科學小組榮譽出品】
building blocks
hunch
chemical properties
strain
compensated for
地球上的生命體需要六種基本元素——碳、氫、氮、氧、硫和磷。這六種元素以及脂肪和蛋白質(zhì)是DNA和RNA的構(gòu)成要素，也就是說，和我們知道的一樣，它們是生命體所必須的。但也許是時候更新這份必需元素目錄了，因為科學家們發(fā)現(xiàn)一種細菌會用砷來代替磷，不需要磷也可生存。因為砷和磷有一些相同的化學特性，研究人員早有預感有這種細菌存在。因此他們從加利福尼亞的莫諾湖收集了一些泥土。莫諾湖水天然帶咸并含砷?；氐綄嶒炇液?，研究人員開始培養(yǎng)泥土中的微生物。但是他們加進去幫助微生物生長的元素并不是磷，而是不同分量的砷。
一種細菌在這種情況下繼續(xù)繁殖，而檢測證實這種生命用砷代替了缺乏的磷合成了它們的DNA。這項發(fā)現(xiàn)刊登在《自然》雜志上。這是人們發(fā)現(xiàn)的第一種可以用其他元素取代生命基本構(gòu)成要素的生物。因此那些在太空尋找生命的天體生物學家們，可不要忽略了那些充滿毒藥的地方哦！:P