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
2024-08-12
26
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] All bacteria follow the growth pattern illustrated in FIGURE 1.
选项
A、TRUE
B、FALSE
答案
A
解析
(文章第四段提到在一个密封的容器里,细菌呈现出一种固定的生长模式。FIGURE 1中的曲线描述的就是细菌生长的一种典型模式。所有的细菌生长都会遵循此种模式。)
转载请注明原文地址:http://tihaiku.com/zcyy/3716139.html
相关试题推荐
"Notuntilsciencebecameprominent______beabolished",somepeopleargue.A、did
Thearmywasseeminglyvictorious,butsincemanypeoplelosttheirlives,itwa
Nowadayspeoplecelebrateallkindsofgraduations.Studentsgraduatefromeleme
Nowadayspeoplecelebrateallkindsofgraduations.Studentsgraduatefromeleme
Nowadayspeoplecelebrateallkindsofgraduations.Studentsgraduatefromeleme
Toridtheworld______,manypeoplebelievethatwemust______somefundamentalc
Peopleoftenlaughwhentheyseepenguinswalking.Penguinslookveryfunnywadd
Peopleoftenlaughwhentheyseepenguinswalking.Penguinslookveryfunnywadd
Peopleoftenlaughwhentheyseepenguinswalking.Penguinslookveryfunnywadd
Peopleoftenlaughwhentheyseepenguinswalking.Penguinslookveryfunnywadd
随机试题
Thereisnotmuchtochoosebetweenmen.Theyareallahotchpotchofgreatn
[originaltext]W:ThisisKerryBurkefromNewYorkDailyNews.(12/13)I’mspeaki
秘书在利用电话进行信息沟通时,若未经授权,则不能告知对方()。A.上司的家庭住
初产妇,40周妊娠,临产6小时,胎膜未破。宫缩间歇4~5分钟,持续30~40秒,
政府发行公债后,如果政府公债的购买者是企业或居民,那么会使社会的信用()。A:等
从一楼走到五楼,爬完一层休息30秒,一共要210秒,那么从一楼走到7楼,需要多少
关于税率的说法中,正确的是( )。A.比例税率是我国运用最广泛的一种税率形式
企业应当在职工实际发生缺勤的会计期间确认与非累积带薪缺勤相关的职工薪酬。()
下列风险分析工具中,风险概率估计的方法中属于定量分析的是()。A.风险结构
根据《建设项目安全设施“三同时”监督管理办法》,在建设项目进行可行性研究阶段,下
最新回复
(
0
)