7.12 病毒起源
Section outline
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Can you "discover" something without actually seeing it?
::你能"发现"的东西 而不实际看到吗?Well, yes you can, and that's precisely how were discovered. Viruses are much smaller than , so special microscopes are needed to see them, but the existence of viruses was known prior to the of these special microscopes.
::嗯,是的,这正是如何被发现的。病毒比病毒小得多, 所以需要特殊的显微镜来观察它们, 但是病毒的存在在这些特别显微镜之前是已知的。Discovery and Origin of Viruses
::病毒的发现和发源Viruses are so small that they can be seen only with an electron . Before electron microscopes were invented, scientists knew viruses must exist. How did they know? They had demonstrated that particles smaller than bacteria cause disease.
::病毒如此之小以至于只能用电子来观察它们。在发明电子显微镜之前,科学家们知道病毒必须存在。他们怎么知道?他们已经证明小于细菌的粒子会造成疾病。Discovery of Viruses
::发现病毒Researchers used special filters to remove bacteria from tissues that were infected. If bacteria were causing the infection, the filtered tissues should no longer be able to make other organisms sick. However, the filtered tissues remained infective. This meant that something even smaller than bacteria was causing the infection.
::研究人员使用特别过滤器将细菌从被感染的组织中除去,如果细菌造成感染,过滤的组织就不应再让其他生物生病,但是过滤的组织仍然感染,这意味着比细菌更小的东西正在造成感染。Scientists did not actually see viruses for the first time until the 1930s. That’s when the electron microscope was invented. The tobacco mosaic virus shown in the Figure was the first one to be seen. In 1915, English bacteriologist Frederick Twort discovered bacteriophage , the viruses that attack bacteria. He noticed tiny clear spots within bacterial colonies, and hypothesized that something was killing the bacteria.
::科学家们直到1930年代才真正第一次看到病毒。 那时,电子显微镜被发明了。 图中显示的烟草混凝土病毒是第一个被看见的病毒。 1915年,英国细菌学家弗雷德里克·图尔特发现了细菌,细菌是攻击细菌的病毒。 他注意到细菌聚居区中的极小的清晰点,并假设细菌正在被某种东西杀死。Tobacco Mosaic Virus. This tobacco mosaic virus was the first virus to be discovered. It was first seen with an electron microscope in 1935. Origin of Viruses
::病毒起源Where did viruses come from? How did the first viruses arise? The answers to these questions are not known for certain. Several hypotheses have been proposed. The two main hypotheses are stated below. Both may be valid and explain the origin of different viruses.
::病毒从何而来? 第一病毒是如何产生的? 这些问题的答案是未知的。 提出了若干假设。 下面将说明两个主要假设。 这两种假设都可能是有效的,并解释不同病毒的起源。-
Small viruses started as runaway pieces of
that originally came from living
such as bacteria.
::小病毒最初是来自细菌等生物的 离家出走的碎片。 -
Large viruses were once parasitic cells inside bigger
host
cells. Over time,
genes
needed to survive and reproduce outside host cells were lost.
::大型病毒曾经是大型宿主细胞中的寄生细胞。 随着时间的推移,在宿主细胞之外生存和繁殖所需的基因丢失了。
Summary
::摘要-
Viruses were assumed to exist before they were first seen with an electron microscope in the 1930s.
::在1930年代首次用电子显微镜看到病毒之前,假定病毒就已经存在。 -
Multiple hypotheses for viral origins have been proposed.
::已经提出了关于病毒来源的多种假设。
Review
::回顾-
Why did scientists think viruses must exist even before they ever saw them with an electron microscope?
::为什么科学家认为病毒必须存在 甚至在他们用电子显微镜 看到病毒之前? -
State two hypotheses for the origin of viruses.
::国家关于病毒来源的两种假设。 -
What allowed scientists to see a virus for the first time?
::是什么让科学家第一次看到病毒?
Resources
::资源 -
Small viruses started as runaway pieces of
that originally came from living
such as bacteria.
