Do you know viruses（病毒） and bacteria（细菌）? Both of them are very small, we can't see them with our eyes, and many people know nothing about them. In fact, there are a number of differences between viruses and bacteria. Bacterium, the singular form of the word bacteria, is a one—celled（单细胞） living thing, with complete sets of both RNA and DNA genetic codes（遗传密码）. For viruses, some are sections of RNA, and the others are sections of DNA. So, bacterium is at least a hundred times larger than a typical virus.
One main difference between viruses and bacteria is the method of reproduction. A bacterium is a completely independent and self—reproducing unit. When the time is right, bacterium will divide its DNA and RNA genetic material in two. This is how bacteria live in almost every environment on Earth, including non—living things like rocks or plastic.
A virus, on the other hand, cannot reproduce without a living host. A virus may lie for thousands of years before finally coming into a suitable host. Once it enters the body of a host, a virus will get in the living cell. Once inside a living cell, a virus takes the place of the living cell's DNA or RNA genetic instructions with its own. Those instructions are usually to make as many copies of the virus as possible.
Ninety—nine percent of all known bacteria are considered useful to humans, or at least have no bad influence. But most viruses, on the other hand, serve no good purpose. Their only purpose is to create more viruses in order to make themselves continue to live.
Bacteria are alive, which means they can be killed by some form of chemical things. Antibiotics（抗生素） can kill bacteria. Viruses, by comparison, are not considered living things. They cannot be 'killed' in the same way as antibiotics kill bacteria. In fact, any medicine is useless for virus' infections. The disease must run its course until the body can make a successful protection on its own.
| Viruses and Bacteria | |||
| Similarity | Both are too smallwith our eyes. | ||
| Differences | Viruses | Bacteria | |
| What they're like | ●They are not living things. | ● They are living things. | |
| ●A virus is a section ofRNADNA. | ●A bacterium has complete sets of both RNA and DNA genetic codes. | ||
| ●A virus is much smaller than a bacterium. | |||
| How they reproduce | A virus cannot make a copy without a living host. | A bacterium can reproducein almost every environment on Earth. | |
| How they influence humans. | Most of them doto humans | Most of them are considered useful to humans, or at least have no bad influence. | |
| for viruses and bacteria | We can use antibiotics to kill bacteria while for viruses it only depends on if our body can make a successful protection on its own. | ||
