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1、 公共英语80篇背诵阅读带翻译(二十四)2Bacteria are extremely small living things. While we measure our own sizes in inches or centimeters, bacterial 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 micron
2、s long, while rounded ones are generally one micron in diameter. Thus if you enlarged a rounded bacterium 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 kilometers) tall. Even with an ordinary microscope, you must
3、 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 flagella. Others
4、 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 glide along over surfaces by some little-understood mechanism. From the bacterial point of view, the world is a very different
5、 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 molecules around them. Bacteria under the microscope, even those with no flagella, often bounce about in the water. This is because
6、 they collide with the water molecules and are pushed this way and that. Molecules move so rapidly that within a tenth of a second the molecules around a bacterium have all been replaced by new ones; even bacteria without flagella are thus constantly exposed to a changing environment. 细菌 细菌是极其微小的生物体
7、。 我们用英寸或厘米来测量自己的大小，而测量细菌却 要用微米。 一微米等于千分之一毫米。 针头直径大约一毫米。 棒状细菌通常有 24 微米 长，而圆形细菌的直径一般只有 1 微米。 因此，即使你把一个圆形细菌放大 1000 倍，它也 不过一个针头那么大。 可是假如把一个成年人放大 1000 倍，就会变成 1 英里(或 1.6 公里) 多高。 用一般的显微镜观看细菌时，你必需认真观看才能观察它们。 使用 100 倍的显微镜 时，你会发觉细菌不过是模糊可见的小细棒或小点点，而它们的构造你却根本看不出来。 使 用特别的着色剂后，你会发觉有的细菌上长着不少波状的“毛发“即鞭毛，而有的细菌只有一 根鞭毛。 鞭毛的旋转可以推动细菌在水中行进。 不少细菌没有鞭毛，因而不能自己行进。 还有些细菌却能通过某些鲜为人知的机制沿物体外表滑动。 我们所熟知的世界在细菌眼中 完全是另一个样子。 对于细菌来说，水就同糖浆之于人类一样稠密。 细菌是如此的微小， 四周化学分子的一举一动都会对它们产生影响。 在显微镜下，细菌，甚至包括那些没有鞭 毛的细菌，常常在水中跳来跳去。 这是由于它们与水分子相撞后，被弹向各个方向。 分子 移动很快速，仅 0.1 秒之隔，一个细菌四周的分子就会完全更新。 因此，即使是没有鞭毛 的细菌也暴露在一个不断变化的环境中。
