问题 问答题 简答题

细菌的芽孢有何实践重要性。产芽孢的细菌主要有哪几类?各举一例。

答案

参考答案:

芽孢是某些细菌在其生长发育后期,,在细胞内形成的一个圆形或椭圆形、壁厚、含水量低、抗屈性强的休眠构造。无繁殖功能,芽孢有极强的抗热抗辐射,抗化学药物和抗静水压等特性。芽孢具有极强的休眠能力,可以保存几年至几十年而不死亡,芽孢的有无、形态和位置,在细菌分类和鉴定中是重要的形态学指标,实践上芽孢的存在亦利于菌种的筛选与保藏,有利于对各种消毒、杀菌措施优劣的判断等。

产芽孢的菌有:革兰氏阳性菌:芽孢杆菌属,梭菌属,芽孢八叠球菌属。革兰氏阴性菌:脱硫肠状菌属。

单项选择题
阅读理解

Researchers have found more evidence that suggests a relationship between races and rates of lung cancer among smokers. A new study shows that black people and Native Hawaiians are more likely to develop lung cancer from smoking. It compared their risk to whites, Japanese-Americans and Latinos.

Researchers at the University of Southern California and the University of Hawaii did the new study. The New England Journal of Medicine published the findings. The eight-year research studied more than 180,000 people. They included present and former smokers and people who never smoked. Almost 2,000 people in the study developed lung cancer.

Researchers say genetics might help explain the racial and ethnic differences. There could be differences in how people's bodies react to smoke. But environmental influences, including the way people smoke, could also make a difference.

African-Americans and Latinos in the study are reported smoking the fewest cigarettes per day. Whites are the heaviest smokers. But the scientists point out that blacks have been reported to breathe cigarette smoke more deeply than white smokers. This could fill their lungs with more of the chemicals in tobacco that cause cancer.

Scientists know that some diseases effect different groups differently. And some drug companies have begun to develop racially targeted medicines. Last June, the United States Food and Drug Administration approved a drug designed to treat heart failure in black patients. The name is BiDil. The agency called it "a step toward the promise of personalized medicine."

小题1:Which of the following orders is from higher to lower risk of having lung cancer?

A.Whites—Native Hawaiians

B.Africans—Americans—Latinos

C.Asians—Native Hawaiians

D.Africans—Americans—Native Hawaiians小题2:Researchers agree that it is _____ that may probably determine black people’s risk of lung cancer.

A.the larger amount of smoking than white people

B.the living style or habit of the blacks

C.the depth of cigarette smoke into their lungs

D.the physical strength to react to cigarette smoke小题3:People in the new study are made up of _____.

A.heavy smokers in America

B.the black and white people

C.the Asians and Hawaiians

D.smokers and non-smokers小题4:The production of BiDil referred to in the last paragraph is to _____.

A.explain different races react to some diseases differently

B.tell the readers that racial differences exist in smokers

C.show a big step people have taken in the medicine area

D.support the idea that it is easy for blacks to have cancers