四級(jí)輔導(dǎo)：英語四級(jí)閱讀（3）

　　NASA-Funded Research Discovers Life Built With Toxic Chemical

　　NASA-funded astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.

　　Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.

　　The definition of life has just expanded， said Ed Weiler， NASAs associate administrator for the Science Mission Directorate at the agencys Headquarters in Washington. As we pursue our efforts to seek signs of life in the solar system， we have to think more broadly， more diversely and consider life as we do not know it.

　　This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth. The research is published in this weeks edition of Science Express.

　　Carbon， hydrogen， nitrogen， oxygen， phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA， the structures that carry genetic instructions for life， and is considered an essential element for all living cells.

　　Phosphorus is a central component of the energy-carrying molecule in all cells （adenosine triphosphate） and also the phospholipids that form all cell membranes. Arsenic， which is chemically similar to phosphorus， is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

　　We know that some microbes can breathe arsenic， but what weve found is a microbe doing something new building parts of itself out of arsenic， said Felisa Wolfe-Simon， a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park， Calif.， and the research teams lead scientist. If something here on Earth can do something so unexpected， what else can life do that we havent seen yet？

　　The newly discovered microbe， strain GFAJ-1， is a member of a common group of bacteria， the Gammaproteobacteria. In the laboratory， the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus， but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.

　　The key issue the researchers investigated was when the microbe was grown on arsenic did the arsenic actually became incorporated into the organisms vital biochemical machinery， such as DNA， proteins and the cell membranes. A variety of sophisticated laboratory techniques was used to determine where the arsenic was incorporated.

　　The team chose to explore Mono Lake because of its unusual chemistry， especially its high salinity， high alkalinity， and high levels of arsenic. This chemistry is in part a result of Mono Lakes isolation from its sources of fresh water for 50 years.

　　The results of this study will inform ongoing research in many areas， including the study of Earths evolution， organic chemistry， biogeochemical cycles， disease mitigation and Earth system research. These findings also will open up new frontiers in microbiology and other areas of research.

　　The idea of alternative biochemistries for life is common in science fiction， said Carl Pilcher， director of the NASA Astrobiology Institute at the agencys Ames Research Center in Moffett Field， Calif. Until now a life form using arsenic as a building block was only theoretical， but now we know such life exists in Mono Lake.

　　The research team included scientists from the U.S. Geological Survey， Arizona State University in Tempe， Ariz.， Lawrence Livermore National Laboratory in Livermore， Calif.， Duquesne University in Pittsburgh， Penn.， and the Stanford Synchroton Radiation Lightsource in Menlo Park， Calif.

　　NASAs Astrobiology Program in Washington contributed funding for the research through its Exobiology and Evolutionary Biology program and the NASA Astrobiology Institute. NASAs Astrobiology Program supports research into the origin， evolution， distribution， and future of life on Earth.

　　「內(nèi)容簡介」

　　文章第一段以一句話簡潔宣布美國宇航局有了科學(xué)新發(fā)現(xiàn)。

　　接著，文章描述了美國宇航局這項(xiàng)發(fā)現(xiàn)的意義。

　　然后，文章也介紹了已知生命的六大基本構(gòu)建元素，而這次新發(fā)現(xiàn)的細(xì)菌的成分如何。詳細(xì)解釋了為什么這是一項(xiàng)全新發(fā)現(xiàn)，并引用了美國宇航局研究員的話語告訴我們這項(xiàng)微生物的不同之處以及生命的未知神奇。

　　最后，文章詳細(xì)介紹了這次發(fā)現(xiàn)的微生物以及該研究成果將來的應(yīng)用領(lǐng)域。

　　「詞匯短語講解」

　?、賑omprise vt. 包括，組成，構(gòu)成 與comprise同樣表示組成、構(gòu)成的詞還有compose、consist等詞，在用法上有一些區(qū)別。

　　comprise是及物動(dòng)詞，后面不需要加介詞；consist則后面要加介詞of，通常指一個(gè)整體由幾部分構(gòu)成，或由某些材料構(gòu)成；compose則一般使用be composed of這種被動(dòng)形式。

　?、谝恍┍乇吵Ｓ脝卧~，harsh adj. 嚴(yán)酷的，刺耳的 conduct v. 引導(dǎo)，帶領(lǐng)，管理，指揮 substitute n. 替代物質(zhì)；代用品 v. 取代，替代。

　　③expand，extend，expend和prolong.這幾個(gè)詞，特別是前面三個(gè)，看起來很像，但意思卻有些差別。

　　expand是膨脹、擴(kuò)大的意思，既可指體積等的擴(kuò)大，也可用于指野心、欲望的膨脹。

　　extend 擴(kuò)展、延伸的意思，是長度或范圍的擴(kuò)展、延伸。 extend ones business 擴(kuò)大營業(yè) extend ones congratulations to 向祝賀

　　expend是花費(fèi)的意思，expensive就是從它演變而來的。

　　prolong 通常表示時(shí)間的延長。

　?、躨n residence 住在某處的 這里引申為屬于某機(jī)構(gòu)的。

　　⑤in part 部分地

　?、辀uilding block 積木，基礎(chǔ)部分

　　「快速閱讀支招」

　　科學(xué)類文章因?yàn)樯婕翱茖W(xué)研究，有很多生物化學(xué)名詞，我們?cè)陂喿x中不必糾結(jié)于這么多專有名詞，關(guān)鍵是弄清楚文章意思，了解一些常用詞。在閱讀文章前要先掃視一遍問題，帶著問題去讀，不然這么長篇幅的文章里可能最后都會(huì)因?yàn)闊┰甓x不下去。

　　另外，這類文章中，通常有很多長句，包括從句、倒裝、強(qiáng)調(diào)等語法運(yùn)用。我們?cè)陂喿x時(shí)要嘗試自己劃分主要成分，根據(jù)這些主干部分了解句子意思。

　　NASA-Funded Research Discovers Life Built With Toxic Chemical

　　NASA-funded astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.

　　Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.

　　The definition of life has just expanded， said Ed Weiler， NASAs associate administrator for the Science Mission Directorate at the agencys Headquarters in Washington. As we pursue our efforts to seek signs of life in the solar system， we have to think more broadly， more diversely and consider life as we do not know it.

　　This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth. The research is published in this weeks edition of Science Express.

　　Carbon， hydrogen， nitrogen， oxygen， phosphorus and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA， the structures that carry genetic instructions for life， and is considered an essential element for all living cells.

　　Phosphorus is a central component of the energy-carrying molecule in all cells （adenosine triphosphate） and also the phospholipids that form all cell membranes. Arsenic， which is chemically similar to phosphorus， is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

　　We know that some microbes can breathe arsenic， but what weve found is a microbe doing something new building parts of itself out of arsenic， said Felisa Wolfe-Simon， a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park， Calif.， and the research teams lead scientist. If something here on Earth can do something so unexpected， what else can life do that we havent seen yet？

　　The newly discovered microbe， strain GFAJ-1， is a member of a common group of bacteria， the Gammaproteobacteria. In the laboratory， the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus， but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.

　　The key issue the researchers investigated was when the microbe was grown on arsenic did the arsenic actually became incorporated into the organisms vital biochemical machinery， such as DNA， proteins and the cell membranes. A variety of sophisticated laboratory techniques was used to determine where the arsenic was incorporated.

　　The team chose to explore Mono Lake because of its unusual chemistry， especially its high salinity， high alkalinity， and high levels of arsenic. This chemistry is in part a result of Mono Lakes isolation from its sources of fresh water for 50 years.

　　The results of this study will inform ongoing research in many areas， including the study of Earths evolution， organic chemistry， biogeochemical cycles， disease mitigation and Earth system research. These findings also will open up new frontiers in microbiology and other areas of research.

　　The idea of alternative biochemistries for life is common in science fiction， said Carl Pilcher， director of the NASA Astrobiology Institute at the agencys Ames Research Center in Moffett Field， Calif. Until now a life form using arsenic as a building block was only theoretical， but now we know such life exists in Mono Lake.

　　The research team included scientists from the U.S. Geological Survey， Arizona State University in Tempe， Ariz.， Lawrence Livermore National Laboratory in Livermore， Calif.， Duquesne University in Pittsburgh， Penn.， and the Stanford Synchroton Radiation Lightsource in Menlo Park， Calif.

　　NASAs Astrobiology Program in Washington contributed funding for the research through its Exobiology and Evolutionary Biology program and the NASA Astrobiology Institute. NASAs Astrobiology Program supports research into the origin， evolution， distribution， and future of life on Earth.

　　「內(nèi)容簡介」

　　文章第一段以一句話簡潔宣布美國宇航局有了科學(xué)新發(fā)現(xiàn)。

　　接著，文章描述了美國宇航局這項(xiàng)發(fā)現(xiàn)的意義。

　　然后，文章也介紹了已知生命的六大基本構(gòu)建元素，而這次新發(fā)現(xiàn)的細(xì)菌的成分如何。詳細(xì)解釋了為什么這是一項(xiàng)全新發(fā)現(xiàn)，并引用了美國宇航局研究員的話語告訴我們這項(xiàng)微生物的不同之處以及生命的未知神奇。

　　最后，文章詳細(xì)介紹了這次發(fā)現(xiàn)的微生物以及該研究成果將來的應(yīng)用領(lǐng)域。

　　「詞匯短語講解」

　　①comprise vt. 包括，組成，構(gòu)成 與comprise同樣表示組成、構(gòu)成的詞還有compose、consist等詞，在用法上有一些區(qū)別。

　　comprise是及物動(dòng)詞，后面不需要加介詞；consist則后面要加介詞of，通常指一個(gè)整體由幾部分構(gòu)成，或由某些材料構(gòu)成；compose則一般使用be composed of這種被動(dòng)形式。

　?、谝恍┍乇吵Ｓ脝卧~，harsh adj. 嚴(yán)酷的，刺耳的 conduct v. 引導(dǎo)，帶領(lǐng)，管理，指揮 substitute n. 替代物質(zhì)；代用品 v. 取代，替代。

　?、踖xpand，extend，expend和prolong.這幾個(gè)詞，特別是前面三個(gè)，看起來很像，但意思卻有些差別。

　　expand是膨脹、擴(kuò)大的意思，既可指體積等的擴(kuò)大，也可用于指野心、欲望的膨脹。

　　extend 擴(kuò)展、延伸的意思，是長度或范圍的擴(kuò)展、延伸。 extend ones business 擴(kuò)大營業(yè) extend ones congratulations to 向祝賀

　　expend是花費(fèi)的意思，expensive就是從它演變而來的。

　　prolong 通常表示時(shí)間的延長。

　?、躨n residence 住在某處的 這里引申為屬于某機(jī)構(gòu)的。

　?、輎n part 部分地

　?、辀uilding block 積木，基礎(chǔ)部分

　　「快速閱讀支招」

　　科學(xué)類文章因?yàn)樯婕翱茖W(xué)研究，有很多生物化學(xué)名詞，我們?cè)陂喿x中不必糾結(jié)于這么多專有名詞，關(guān)鍵是弄清楚文章意思，了解一些常用詞。在閱讀文章前要先掃視一遍問題，帶著問題去讀，不然這么長篇幅的文章里可能最后都會(huì)因?yàn)闊┰甓x不下去。

　　另外，這類文章中，通常有很多長句，包括從句、倒裝、強(qiáng)調(diào)等語法運(yùn)用。我們?cè)陂喿x時(shí)要嘗試自己劃分主要成分，根據(jù)這些主干部分了解句子意思。