考研背诵50篇——48 Bacteria

 　　Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial¹ size is measured in microns. One micron is a thousandth of a millimeter: a pinhead is about a millimeter across. Rod-shaped bacteria are usually from two to four microns long, while rounded ones are generally one micron in diameter. Thus if you enlarged a rounded bacterium² a thousand times, it would be just about the size of a pinhead. An adult human magnified by the same amount would be over a mile(1.6 kilometer) tall.

 

　　Even with an ordinary microscope, you must look closely to see bacteria. Using a magnification of 100 times, one finds that bacteria are barely visible as tiny rods or dots. One cannot make out anything of their structure. Using special stains, one can see that some bacteria have attached to them wavy-looking "hairs" called flagella³. Others have only one flagellum. The flagella rotate, pushing the bacteria through the water. Many bacteria lack flagella and cannot move about by their own power, while others can glide⁴ along over surfaces by some little-understood mechanism⁵.

 

　　From the bacteria point of view, the world is a very different place from what it is to humans. To a bacterium water is as thick as molasses is to us. Bacteria are so small that they are influenced by the movements of the chemical molecules⁶ around them. Bacteria under the microscope, even those with no flagella, often bounce about in the water. This is because they collide with the watery⁷ molecules and are pushed this way and that. Molecules move so rapidly that within a tenth of a second the molecules around a bacteria have all been replaced by new ones; even bacteria without flagella are thus constantly exposed to a changing environment.

1 bacterial   

a.细菌的

参考例句：

• Bacterial reproduction is accelerated in weightless space. 在失重的空间，细菌繁殖加快了。
• Brain lesions can be caused by bacterial infections. 大脑损伤可能由细菌感染引起。

2 bacterium   

n.(pl.)bacteria 细菌

参考例句：

• The bacterium possibly goes in the human body by the mouth.细菌可能通过口进入人体。
• A bacterium is identified as the cause for his duodenal ulcer.一种细菌被断定为造成他十二指肠溃疡的根源。

3 flagella   

n.鞭节，鞭毛

参考例句：

• The rotation of flagella pushes the bacteria through the water.鞭毛的旋转可以推动细菌在水中行进。
• Many protoctistans are motile,using pseudopodia,cilia or flagella.许多原生动物利用伪足、纤毛或鞭毛能运动。

4 glide   

n./v.溜，滑行；(时间)消逝

参考例句：

• We stood in silence watching the snake glide effortlessly.我们噤若寒蝉地站着，眼看那条蛇逍遥自在地游来游去。
• So graceful was the ballerina that she just seemed to glide.那芭蕾舞女演员翩跹起舞，宛如滑翔。

5 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

6 molecules   

分子( molecule的名词复数 )

参考例句：

• The structure of molecules can be seen under an electron microscope. 分子的结构可在电子显微镜下观察到。
• Inside the reactor the large molecules are cracked into smaller molecules. 在反应堆里，大分子裂变为小分子。

7 watery   

adj.有水的，水汪汪的；湿的，湿润的

参考例句：

• In his watery eyes there is an expression of distrust.他那含泪的眼睛流露出惊惶失措的神情。
• Her eyes became watery because of the smoke.因为烟熏，她的双眼变得泪汪汪的。