Bacterial Quorum SensingBacteria(细菌)play an i...

Bacterial Quorum Sensing

Bacteria(细菌)play an important role in our lives. They can keep us alive as well as make us sick. It wasn’t until fairly recently that we learned bacteria can communicate with one another.

In the 1960s, researchers found that a kind of bacteria called Vibrio fischeri（费氏弧菌） produced no light when they were alone, but that they exhibited great amount of light as the bacterial population grew to a certain number. How did this happen? How can Vibrio fischeri tell the difference between times when they’re alone and times when they’re in a community, and then all do something together?

Researchers found they talk to each other with a chemical language—signal molecules(信号分子). Vibrio fischeri makes signal molecules, and it also has a receptor on its surface that fits like a lock and key with a signal molecule. As the bacteria increase, more and more signal molecules are sent into the environment. When signal molecules increase to a certain amount, they lock down into those receptors and information comes into the bacteria, which tells them how many neighbors there are. As soon as they realize the population has hit the certain number, all of the bacteria behave as a group, making light together. In the past ten years, researchers have found all bacteria have systems like this: they make and recognize chemical words, determine(判断)the size of the community, and carry out tasks that would be unsuccessful if a single one were to act alone. This process is called quorum sensing.

Most of the time, bacteria live with thousands of other species (种类)of bacteria. There has to be a language of interspecies communication. In fact, bacteria have another kind of signal molecule, which is the common language used by all species. Moreover, this kind of molecule has its own receptor. In this way, bacteria are able to count different populations, and then they decide what task to carry out depending on which species has the greatest population.

Knowing how bacteria communicate could influence how we fight disease. What if bacteria can’t talk or hear? They won’t recognize when there are enough bacteria and when to exhibit the group behavior to make us sick. Researchers are developing a method—to make molecules that look like the real ones and then they lock into the receptors to jam recognition of the real situation.

On the other hand, researchers also improve the conversation of the beneficial bacteria, so they can do things that we want them to do better than they would do on their own.

1.According to the passage, what can we learn about quorum sensing?

A.Quorum sensing may happen when there is only one Vibrio fischeri.

B.Signal molecules are kept away from receptors during quorum sensing.

C.Most bacteria have similar systems to make light during quorum sensing.

D.Bacteria carry out a group task when their population hit a certain number.

2.What can we learn from the passage?

A.The more species there are, the more group actions bacteria will take.

B.In different environments, bacteria have different interspecies languages.

C.Beneficial bacteria communicate better by themselves than harmful ones.

D.To fight disease, researchers try to turn off the communication between harmful bacteria.

3.The passage is mainly about ________.

A.why bacterial population grows B.how bacteria communicate with each other

C.which bacteria help fight disease D.what scientists do to find quorum sensing

九年级英语阅读单选中等难度题查看答案及解析

China is playing an important role 　　the development of economy.

A. by         B. in

C. with       D. because

九年级英语单项填空简单题查看答案及解析

Colors play an important role in our world. They have different meanings to people of different cultures. Here are some colors and what they represent to various people of the world.

Red is the favorite color of brides in Vietnam. In this country, red represents fortune, success, and good luck. In China red is a symbol of luck and is used for many celebrations such as weddings and the beginning of the new year. In India red is a symbol of purity and commitment, and it is used in wedding clothing. In the United States red represents love and is used during Christmas and Valentine's Day. Red also represents speed and power in the west, which is why it is a popular color for race cars and toy rockets.

In Paris, all garbage collectors are clothed in green. They drive green trucks and dispose of waste in green bins. In many parts of the world, green has become a symbol of kindness to the earth. In Ireland, green symbolizes Catholicism, and in India it is the color of Islam.

Yellow is the color that symbolizes the sun. Yellow can make people feel happy and excited, but at the same time can make people feel angrier or more frustrated. In the United States, school buses and taxicabs are often yellow, because you can see this color ruore easily. In Japan, yellow is the color of bravery.

To the Japanese, Chinese, Vietnamese and Koreans, white symbolizes death. To people of India and in the west white is a color of purity.

根据材料内容选择最佳答案，并将其标号填人题前括号内。

1.How many colors are mentioned in the article?

A.Three　　 B.Four　　 C.Five　　 D.Six

2.What does the underline word”represent”mean in the passage?

A.代表　　 B.承认　　 C.接受　　 D.说明

3.Who regards red as a symbol of luck?

A.The Indians　　 B.The Japaness

C.The Chinese　 　　 D.The Americans

4.A person will be even angrier when he sees_____

A.red　　 B.green　　 C.yellow　　 D.white

5.Which of the flowing is true?

A.Red symbolizes the sun in most countries.

B.In the USA,school bus and taxis are often yellow.

C.In Ireland,all garbage collectos were green clothes.

D.Tothe Koreans,white is a color of purity.

九年级英语阅读理解中等难度题查看答案及解析

Information Card

九年级英语任务型阅读中等难度题查看答案及解析

Friends play an important role in our life. Most people hope that their friends will always be there. They _____ friendship to last forever. _____， even the best friendship can end.

As time goes by, many friendships end because of a(n) _____ in personality or way of life. The friendship slowly loses importance and finally _____.

Tommy wrote, “I didn't even know the friendship was over until I caught myself thinking of Alan as a former friend.”

Peter explained, “We _____ seeing each other less and less. The friendship was over.”

Sometimes friendships _____ suddenly from a disagreement or moving to another place.

Alice said, “The end of our friendship was a gradual thing. I moved from one side of the city to the other. Since then we _____ made a phone call. We met less and less. At last our friendship ended.”

Jack said, “When I moved to Seattle after college, our friendship died. Both of us were always_____ with new jobs, so we didn't keep _____ touch with each other. Our friendship was so dead that I didn't call him ______ I went home.”

Yet the biggest problem to a friendship is change. Lillian Rubin in her book Just Friends says, “Generally it's ______ that friends will accept each other if they both remain what they were when they met, or change in similar directions. If they change or grow in different ways, the friendship most likely ______ lost.”

No matter why, when, or how friendship ends, there is always ______ pain of loss. When nothing can be ______ to keep the friendship, it is important to forget the pain. Then move on ______ new friendships.

May new friendships bring you pleasure and happiness!

1.A. hope　　 B. expect　　 C. decide　　 D. prefer

2.A. Unfortunately　　 B. Luckily　　 C. Then　　 D. So

3.A. interest　　 B. experience　　 C. change　　 D. suggestion

4.A. forgets　　 B. disappears　　 C. appears　　 D. improves

5.A. finished　　 B. practised　　 C. continued　　 D. started

6.A. break down　　 B. break away　　 C. break off　　 D. break in

7.A. often　　 B. seldom　　 C. always　　 D. never

8.A. struggling　　 B. satisfying　　 C. pleased　　 D. fed

9.A. at　　 B. by　　 C. on　　 D. in

10.A. even if　　 B. while　　 C. before　　 D. since

11.A. strange　　 B. true　　 C. false　　 D. impossible

12.A. will be　　 B. is　　 C. will　　 D. to be

13.A. little　　 B. some　　 C. any　　 D. no

14.A. thought　　 B. checked　　 C. carried　　 D. done

15.A. to ask for　　 B. forming　　 C. to build　　 D. beginning

九年级英语完型填空困难题查看答案及解析

Friends play an important role in our life. Most people hope that their friends will always be there. They 　　　 　 friendship to last forever.　　　 　 , even the best friendship can end.

As time goes by, many friendships end because of a(n) _　　　 　 in personality or way of life. The friendship slowly loses importance and finally_　　　 　 _.

Tommy wrote, “I didn’t even know the friendship was over until I caught myself thinking of Alan as a former friend.”

Peter explained. “We _　　　 　 seeing each other less and less. The friendship was just over.”

Sometimes friendships_　　　 　 _ suddenly from a disagreement or move to another place.

Alice said,　 “The end of our friendship was a gradual thing. I moved from one side of the city to the other. Since then we _　　　 　 made a phone call. We met less and less. At last our friendship ended.”

Jack said, “ When I moved to Seattle after college, our friendship died. Both of us were always_　　　 　 with new jobs, so we didn’t keep _　　　 　 touch with each other. Our friendship was so dead that I didn’t call him _　　　 　 _ I went home.”

Yet the biggest problem to a friendship is change. Lillian Rubin in her book Just Friends say, “Generally it’s _　　　 　 _ that friends will accept each other if they both remain what they were when they met, or change in similar directions. If they change or grow in different ways, the friendship most likely 　　　 　 lost.”

No matter why, when, or how friendships end, there is always _　　　 　 _ pain of loss.　 When nothing can be _　　　 　 to keep the friendship, it is important to forget the pain. Then move on _　　　 　 _ new friendships.

May new friendships bring you pleasure and happiness!

1.A. hope　　　　　　　　　　 B. expect　　　　　　 C. decide　　　　 D. prefer

2.A. Unfortunately　　　　　 B. Luckily　　　　　　　　 C. Then　　　　 D. So

3.A. interest　　　　　　　　 B. experience　　　　 C. change　　　　 D. Suggestion

4.A. forgets　　　　　　　　 B. disappears　　　　　　 C. appears　　　　 D. improves

5.A. finished　　　　　　　　 B. practiced　　　　　　 C. continued　　　　 D. started

6.A. break down　　　　　　 B. break away　　　　　　 C. break off　　　　 D. break in

7.A. often　　　　　　　　　 B. seldom　　　　　　 C. always　　　　 D. never

8.A. struggling　　　　　　 B. satisfying　　　　 C. pleased　　　　 D. fed

9.A. at　　　　　　　　　　　 B. by　　　　　　　　 C. on　　　　　　　 D. in

10.A. even if　　　　　　　　 B. while　　　　　　 C. before　　　　　 D. since

11.A. strange　　　　　　　　 B. true　　　　　　 C. false　　　　　 D. impossible

12.A. will be　　　　　　　　 B. is　　　　　　　　 C. will　　　　　 D. to be

13.A. little　　　　　　　　　　 B. some　　　　　　　 C. any　　　　　　 D. no

14.A. thought　　　　　　　　 B. checked　　　　　　 C. carried　　　　 D. done

15.A. to ask for　　　　　　　 B. forming　　　　 C. to build　　　　 D. beginning

九年级英语完形填空极难题查看答案及解析

Friends play an important role in our life. Most people hope that their friends will always be there. They _____ friendship to last forever. ____, even the best friendship can end.

As time goes by, many friendships end because of a(n) ______ in personality or way of life. The friendship slowly loses importance and finally_______.

Tommy wrote, “I didn’t even know the friendship was over until I caught myself thinking of Alan as a former friend.”

Peter explained. “We _____ seeing each other less and less. The friendship was just over.”

Sometimes friendships______ suddenly from a disagreement or move to another place.

Alice said,　 “The end of our friendship was a gradual thing. I moved from one side of the city to the other. Since then we _____ made a phone call. We met less and less. At last our friendship ended.”

Jack said, “ When I moved to Seattle after college, our friendship died. Both of us were always____ with new jobs, so we didn’t keep _____ touch with each other. Our friendship was so dead that I didn’t call him_____ I went home.”

Yet the biggest problem to a friendship is change. Lillian Rubin in her book Just Friends say, “Generally it’s______ that friends will accept each other if they both remain what they were when they met, or change in similar directions. If they change or grow in different ways, the friendship most likely______ lost.”

No matter why, when, or how friendships end, there is always_____ pain of loss.　 When nothing can be____ to keep the friendship, it is important to forget the pain. Then move on_____ new friendships.

May new friendships bring you pleasure and happiness!

1.A. hope　　　　　　　　 B. expect　　　　　　　 C. decide　　　　　　　 D. prefer

2.A. Unfortunately　　　　 B. Luckily　　　　　　 C. Then　　　　　　　　 D. So

3.A. interest　　　　　　　 B. experience　　　　　 C. change　　　　　　 D. Suggestion

4.A. forgets　　　　　　　 B. disappears　　　　　　 C. appears　　　　　　 D. improves

5.A. finished　　　　　　 B. practiced　　　　　　 C. continued　　　　　　 D. started

6.A. break down　　　　 B. break away　　　　　 C. break off　　　　　　 D. break in

7.A. often　　　　　　　　 B. seldom　　　　　　　　 C. always　　　　　　　 D. never

8.A. struggling　　　　　 B. satisfying　　　　　　 C. pleased　　　　　　 D. fed

9.A. at　　　　　　　　　　 B. by　　　　　　　　　　 C. on　　　　　　　　　　 D. in

10.A. even if　　　　　　 B. while　　　　　　　　 C. before　　　　　　　 D. since

11.A. strange　　　　　　 B. true　　　　　　　　　 C. false　　　　　　　　 D. impossible

12.A. will be　　　　　　 B. is　　　　　　　　　　 C. will　　　　　　　　 D. to be

13.A. little　　　　　　　　 B. some　　　　　　　　 C. any　　　　　　　　 D. no

14.A. thought　　　　　　 B. checked　　　　　　 C. carried　　　　　　　 D. done

15.A. to ask for　　　　　 B. forming　　　　　　 C. to build　　　　　　 D. beginning

九年级英语完型填空困难题查看答案及解析

The taxi plays an important role in Britain. When thinking of London, many image （形象）come to mind: Big Ben, the Ferris Wheel（摩天轮），red telephone boxes…and black London taxis.

But what is so special about a simple taxi? First of all, in shape and style, a London taxi is very different from an ordinary one. It looks like a half-car and half-van（半厢式货车）. It has plenty of room in the back. That means it’s easy for disabled people to use. And the black color makes it special on the road.

Besides, taxi drivers play an important part in your travel. They have to pass a taxi driving test, and in London it is very difficult. As there are many tourists in London, drivers must know many roads by memory.

Apart from（除此之外）driving you to your destination, it is normal for the driver and the passenger to have a conversation. A taxi is a social space which the driver and you share. The image of a London taxi driver is one that friendly and talkactive. Every time I take a taxi, I ask how the driver is. Then we usually talk about sports or news events.

1. A London taxi has plenty of room in the back, so 　　　　 .

A. it is an ordinary car

B. it is easy for disabled people to use

C. the taxi driver is talkactive

D. the taxi driver can drive faster

2.What does the third paragraph mainly talk about?

A. taxi shape　　　　 　　 B. taxi style

C. taxi drivers　　　　　　 D. taxi conversation

3.In the fourth paragraph, the underlined word “destination” means 　　　　 in Chinese.

A. 地点　　　　　　　 B. 目的地　　　　　　　 C. 居住地　　　　　　　　 D. 地区

4. What do the drivers usually talk about with the travelers?

A. only sports　　　　　　　　　　　　 B. only new events.

C. ages and hobbies　　　　　　　　　 D. sports or news events

5.According to the passage, we can infer it’s 　　　　 for tourists to take a taxi in London.

A. dangerous　　　　　　 B. difficult

C. comfortable　　　　 D. boring

九年级英语阅读理解困难题查看答案及解析

A class teacher, in my opinion, plays an important role in a child’s development. Every year when my daughter moves to a new class, I have a usual big worry –her new class teacher. This year, she is moving to Class Three and I can’t wait to see how things are going on.

Last year, my daughter did not like her teacher at all. It was so bad that she did not look forward to school. It was a year full of trouble and worries.

This year, Miss Purity is gentle and humorous. It’s hard not to like her. Here are the changes in my daughter.

She becomes an early bird. Last year, mornings were like a fight because I had to force Tasha to hurry up when she was preparing for school. I had to pull her out of bed, tell her to take breakfast and then drove her to school. But now, our mornings are like a party. She wakes up early, prepares everything at a high speed and then rushes to school to be with Miss Purity.

She’s happy. She enjoys school and school work and keeps talking about what they did at school when she comes home.

She’s responsible. She used to be careless and forgetful. But now she never forgets even her water bottle at school. She makes her bed and helps in the kitchen.

Her diary is full of praises. The diary is the tool of communication between the teacher and the parents. Last year, her diary was always full of negative reports. One time, she poured water in a child’s lunchbox, another time she threw another kid’s textbook in the toilet. Now she began to share her snacks with those who did not have anything. She’s always volunteering to clean the blackboard, the teacher’s chair and desk.

She does well in school. Finishing her classwork was such a big problem. She had to do it at home. But now, she finished both the classwork and homework at school.

1.What is the big worry of Tasha’s father every year?

A.Who will be Tasha’s class teacher. B.Which class Tasha will be in.

C.How Tasha goes to school in the morning. D.What Miss Purity looks like.

2.What did Tasha do when she didn’t like her class teacher?

A.She had a fight with her mother in the morning. B.She didn’t want to go to school.

C.She missed a lot of classes. D.She refused to do classwork and homework.

3.What does “early bird” mean in the passage?

A.It is a lovely little child. B.It is the most beautiful bird.

C.It is someone who lives alone. D.It is someone who gets up early.

4.Which of the following is not true about Tasha’s past?

A.She couldn’t finish her classwork at school. B.She often forgot things at school.

C.She didn’t get on well with her classmates. D.She was careless and silent.

5.What is not mentioned about the changes in Tasha.

A.The progress with Miss Purity B.Her hobbies

C.Her habit of living D.Her behaviors at school.

九年级英语阅读单选中等难度题查看答案及解析

________ some disadvantages are seen, China’s health systems have played an important role in dealing with the outbreak of NCP.

A.If B.Unless C.Though

九年级英语单选题中等难度题查看答案及解析