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
2023-10-15
57
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°C and 45°C.
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.
Questions 56 to 60
Mark each statement as either true(T)or false(F)according the passage. [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/3101005.html
相关试题推荐
Severalcenturiesago,whenEuropeanpeoplemarveledatthefinepotteryshi
Severalcenturiesago,whenEuropeanpeoplemarveledatthefinepotteryshi
Severalcenturiesago,whenEuropeanpeoplemarveledatthefinepotteryshi
Whatwillcitylifebelikeinthefuture?Somepeoplethinkthatlifeinth
Whatwillcitylifebelikeinthefuture?Somepeoplethinkthatlifeinth
Whatwillcitylifebelikeinthefuture?Somepeoplethinkthatlifeinth
“Notuntilsciencebecameprominent______beabolished”,somepeopleargue.A、did
efficientthemdisapprovepersonappearPeoplewhoareu
efficientthemdisapprovepersonappearPeoplewhoareu
efficientthemdisapprovepersonappearPeoplewhoareu
随机试题
WhatistheMandoing?[br][originaltext]M:WhatcanIdoifIcan’tfinishrea
Theentrepreneurhadawell-deservedreputationfor______,havingaccuratelyant
All______isacontinuoussupplyofthebasicnecessitiesoflife.A、whatisnee
对于单位阶跃输入,下列说法不正确的是()。A.只有0型系统具有稳态误差,其大小与
地籍管理信息系统的信息查询方式主要有( )。A.指定专题进行简单查询 B.指
下列隧道中,应在洞口外合适位置设置联络通道,以便紧急情况时车辆转换是()。
下面谱例用了哪种对位技术? A.对比 B.倒影 C.逆行 D.变奏
既能解表散寒、通窍止痛,又能燥湿止带、消肿排脓的是A:细辛B:荆芥C:川芎
根据《水利工程基本建设项目竣工决算审计规程》,竣工决算审计是()的重要依据。A
关于慢性肾盂肾炎的临床表现,下列哪项是错误的A.尿路刺激征可不典型 B.轻度水
最新回复
(
0
)