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
38
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 organ-isms. 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______.
选项
答案
20℃and 45℃
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/3102358.html
相关试题推荐
Howmanypeoplehavejumpedintothewater?[originaltext]Rescuersaresearching
Changesinthewaypeoplelivebringaboutchangesinthejobsthattheydo.Mor
Changesinthewaypeoplelivebringaboutchangesinthejobsthattheydo.Mor
Changesinthewaypeoplelivebringaboutchangesinthejobsthattheydo.Mor
Changesinthewaypeoplelivebringaboutchangesinthejobsthattheydo.Mor
Changesinthewaypeoplelivebringaboutchangesinthejobsthattheydo.Mor
After1945,theUSgovernmentbuiltmanynewroadsandhighways.Peoplemo
After1945,theUSgovernmentbuiltmanynewroadsandhighways.Peoplemo
After1945,theUSgovernmentbuiltmanynewroadsandhighways.Peoplemo
WhatisthepolitewaytoaddressThaipeople?[br][originaltext]M:Sowhatkin
随机试题
Areorganicallygrownfoodsthebestfoodchoices?Theadvantagesclaimedfo
[originaltext]ISTANBUL,Turkey—Near-simultaneousexplosionshittwoIstanbu
(1)AnothermilestoneonthejourneytowardsdigitalcashwaspassedonNovem
患者,男,30岁。出租车司机。因黑色稀便3天入院,3天来,每天排黑色稀便2次,每
慢性肾衰竭首发症状是A:高血压 B:贫血 C:食欲缺乏 D:水肿 E:肾
素质教育中全面加强和改进德育、智育、体育、美育,坚持文化知识学习和思想品德修养的
某宗房地产的价格并不是由其开发建设成本决定的,因此运用成本法估价应该注意的内容包
某知名家用电器公司每年都要招聘一定数量的应届毕业生,该公司选拔人才时,通常用笔试
新产品开发战略的核心内容是确定企业新产品开发的领域、新产品开发的目标、达成目标的
理中丸的功能为A.温胃理气 B.温中散寒,健胃 C.温中补虚,缓急止痛 D
最新回复
(
0
)