首页
登录
职称英语
Most people consider bacteria dangerous. After all, these microorganisms cau
Most people consider bacteria dangerous. After all, these microorganisms cau
游客
2023-10-16
51
管理
问题
Most people consider bacteria dangerous. After all, these microorganisms cause a host of serious human diseases, including tuberculosis, typhoid fever, pneumonia, and food poisoning. In fact, however, only a small percentage of bacteria cause diseases, while many bacteria are actually beneficial to humans. For example, doctors use bacteria to produce vaccines and other medicines. Bacteria are also critical to many industrial processes, from fermenting wine to recycling wastes, and scientists use bacteria to study many of the biological processes common to all living things.
With such a wide variety of economic and scientific applications, it is no surprise that several laboratories around the United States grow and sell bacteria as a crop. These laboratories use specialized farming techniques to produce one of the nation’s most valuable biological commodities.
Like plants, bacteria have specific growth requirements. In particular, they need a place to grow and they need a supply of nutrients. Bacteria may be cultivated in containers ranging from small test tubes to giant steel tanks. The organisms are placed in a container along with a nutritionally balanced liquid or jelly, called a culture medium, which provides vitamins, minerals, and fluids to the growing bacteria. The growth container and culture medium must be kept at a constant temperature that is appropriate for the type of bacteria being cultivated. Most bacteria used in medicine and industry grow best between 20℃ and 45℃.
In a closed container, bacteria exhibit a definite growth pattern. The figure shows a typical bacterial growth curve. All bacteria follow this pattern, a fact that is very important to anyone who wants to cultivate them in large numbers.
When bacteria are first placed in a growth container, they must adapt to their new environment, and growth is slow while they are making this adjustment. This period is called the "start phase" of the bacterial growth cycle. At the end of this phase, as the bacteria become accustomed to their new living conditions, they begin to grow and reproduce rapidly. During the second phase, called the "log phase," a population explosion occurs. In a large tank, millions of new bacteria may be produced every hour during this phase. Eventually, however, the bacterial population reaches the maximum size possible, given the limitations of the growth container. At this point, the bacteria enter the "stationary growth phase," during which they continue to reproduce, but at a slower rate. After a time, the bacteria use up their supply of nutrients and their wastes accumulate in the growth container. The final period in the growth cycle, called the "death phase," occurs when the bacteria begin to die faster than they reproduce.
People who grow bacteria for science and industry take advantage of this unique growth cycle. Bacteria are harvested during the "stationary growth phase," yielding a good crop of usable organisms. By carefully monitoring the growth pattern, bacteria farmers can also decide when to add more nutrients to the culture medium or to transfer the bacteria to new growth containers. In this way, they can prevent large losses during the "death phase." By applying a knowledge of the growth requirements and patterns of bacteria, these modern-day agriculturalists are able to help everyone derive the maximum benefit from these versatile organisms. [br] Most people consider bacteria dangerous, actually, most of them are ______.
选项
答案
beneficial to humans
解析
(文章第一段指出大多数人认为细菌是危险的,但事实上只有一小部分的细菌会致病,而大多数的细菌对人体是有益的。)
转载请注明原文地址:https://tihaiku.com/zcyy/3102994.html
相关试题推荐
Afewyearsago,peopleinEnglandvotedforthegreatestpersonofalltime
Novels,magazines,andnewspapers—manypeoplereadtheseintheirsparetime
Novels,magazines,andnewspapers—manypeoplereadtheseintheirsparetime
Novels,magazines,andnewspapers—manypeoplereadtheseintheirsparetime
Novels,magazines,andnewspapers—manypeoplereadtheseintheirsparetime
Novels,magazines,andnewspapers—manypeoplereadtheseintheirsparetime
Asthesupplyofgeneticallymodified(GM)foodincreases,manypeopleareun
Asthesupplyofgeneticallymodified(GM)foodincreases,manypeopleareun
Noteverypersonisalike.Mostpeoplehaveverydifferenttalents.Somepeople
[img]2019m9x/ct_eyyjsdz2019j_eyyjsdreadd_0184_201909[/img]Manypeoplecompla
随机试题
Learningdoesnothappenpassively.Itisanactivitywhichapersondoes.I
[originaltext]W:Iamreallydiscouragedbythelackofprogressmystaffisma
女性,18岁,咳嗽4个月,伴低热,1个月前左膝部外伤,体格检查:跛行,左股四头肌
案例数学法的主要目的在于引发学生听课的兴趣。( )
关于热原的性质分别是 A.不挥发性 B.不耐强酸强碱性 C.耐热性 D.
下列哪项是糖尿病酮症酸中毒最特异性的临床表现A.多饮、多尿、疲乏 B.食欲不振
2022年1月20日,国家能源局发布的最新数据显示,截至2021年底,我国(
技术分析的缺点有()。?A.信号滞后 B.技术陷阱随时出现 C.各种指标经
某药物体内过程符合药物动力学单室模型,药物消除按一级速率过程进行,静脉注射给药后
正中牙合位是指A:韧带位 B:后退位 C:牙尖交错位 D:直立姿势位 E
最新回复
(
0
)