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
5
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 bacteria used in medicine and industry grow best between the temperature of 20 °F and 45°F.
选项
A、TRUE
B、FALSE
答案
B
解析
(文章第三段最后一句话明确指出Most bacteria used in medicine and industry grow best between 20℃and 45℃。)
转载请注明原文地址:https://tihaiku.com/zcyy/3716138.html
相关试题推荐
HolmesandWatsonhadapprehendedthreepeopleonsuspicionofshoplifting.The
Mostpeopleconsiderbacteriadangerous.Afterall,thesemicroorganismscau
Mostpeopleconsiderbacteriadangerous.Afterall,thesemicroorganismscau
PeopleintheUnitedStatesinthenineteenthcenturywerehauntedbythepr
PeopleintheUnitedStatesinthenineteenthcenturywerehauntedbythepr
Withtherecentscandalinmind,wouldyouadvisepeoplewhohave______intheir
SomepeoplebelievethatprivatecarsshouldbeencouragedinChina.Othersargu
Whenreadingamagazine,mostpeopleskimitfirst,readingaparagraphortwo.
当重大的危机发生时,人们往往会采取这两种策略之一:对抗或逃脱。(turnto)Intimesofgreatcrises,peopleoftentu
Manypeopleare______airbornepollutantssuchaspollen.______,scientificres
随机试题
ItisnotthefirsttimethatI______byhimduringmycooperationwithhim.A、wa
从整个20世纪历史过程看,国际政治关系的内容基本上由()构成。A.各国际政治主体
因特网最高层域名分为机构性域名和地理性域名两大类,目前主要有14种机构性域名,其
在施工质量处理过程中,按照施工验收规范和相关的质量标准,并结合实际量测、试验和检
《中华人民共和国国歌法》于2017年10月1日起施行。该法是为了维护国歌的尊严,
A.2000 B.500 C.1000 D.250
维生素C又名( )。A.硫胺素 B.胡萝卜素 C.抗坏血酸 D.叶酸
多瓶组单元独立内贮压式七氟丙烷气体灭火系统的组件不包括()。A.信号反馈装置
当过去感知过、思考过或体验过的事物重新出现时,我们能够识别出来的心理现象叫((
隧道防排水包含()。A.结构防排水、特殊防排水 B.结构防排水、施工防排水
最新回复
(
0
)