课程咨询

托福考试网 托福资料下载 托福资讯 0元讲座 水平测试

托福考试练习
新东方在线 > TOEFL > 托福听力 > 正文
托福培训

扫码免费领资料

内含托福全科备考资料

更有免费水平测试及备考规划

托福培训

扫码关注掌握一手留学资讯

回复XDF免费水平测试

录播精讲 直播课HOT

托福听力练习-科学美国人60秒:细菌基本构成元素

2017-06-10 09:27:00来源：科学美国人60秒

点击查看>>科学美国人60秒音频：细菌基本构成元素

　　科学美国人60秒听力练习：细菌基本构成元素

　　科学美国人60秒英文文本

　　A bacterium has been discovered that can substitute arsenic for phosphorus in fundamental life chemistry. Christopher Intagliata reports

　　Life on Earth requires six basic ingredients—carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus. Those six elements are the building blocks 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 hunch a bug like this might exist, because arsenic has some chemical properties 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 strain continued to thrive. And tests confirmed that the organisms compensated for the lack of phosphorus by building their DNA with arsenic instead. The research appears in the journal Science. [Felisa Wolfe-Simon et al., "A Bacterium That Can Grow by Using Arsenic Instead of Phosphorus"]

　　This is the first known life form that seems to be able to swap out one of life's fundamental building blocks with another element. So for astrobiologists hunting for life in space, don’t rule out places filled with poison.

　　—Christopher Intagliata

　　中文翻译请点击下一页

本文关键字: 托福听力 科学美国人60秒

上一页 1 2 下一页

托福辅导

关注新东方在线托福

托福机经·Official题目练习

考前重点突破·听说读写海量资料

更多资料

关注新东方在线托福，
回复【XDF】获取大礼包

托福辅导
  • 1.打开手机微信【扫一扫】，识别上方二维码；
  • 2.点击【添加】，回复对应关键字领取学习资料。
更多>>
更多内容

免费获取托福备考大礼包

微信扫描下方二维码 立即领取

托福辅导
更多>>
更多公益讲座>>
更多>>
更多资料
托福TPO 托福听力练习 托福口语练习 托福阅读练习 托福写作练习
我要
反馈 返回
首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10