首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Most people consider bacteria dangerous. After all, these microorganisms cause a host of serious human diseases, including tuber
Most people consider bacteria dangerous. After all, these microorganisms cause a host of serious human diseases, including tuber
admin
2016-12-08
61
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.
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:https://kaotiyun.com/show/GZAK777K
本试题收录于:
B类竞赛(英语专业本科专科)题库大学生英语竞赛(NECCS)分类
0
B类竞赛(英语专业本科专科)
大学生英语竞赛(NECCS)
相关试题推荐
Thewritersofmurderstoriesgotoagreatdealoftroubletokeepusguessingrightuptotheend.Inactualfact,peopleofte
Thewritersofmurderstoriesgotoagreatdealoftroubletokeepusguessingrightuptotheend.Inactualfact,peopleofte
Manyayoungpersontellsmehewantstobeawriter.Ialwaysencouragesuchpeople,butIalsoexplainthatthere’sabigdiff
What’sTania’sphonenumber?
许多插图画家只好亲自学习电脑制图。(resign,manya)
Fillinthemissingnumbersinthissequence;15,873x7=111,11115,873x14=222,22215,873x(a)=333,33315(b)x28=(c)4
唯一重要的事情就是要平安回家。(matter)
Ifitweretwohourslater,itwouldbehalfaslonguntilmidnightasitwouldbeifitwereanhourlater.Whattimeisitnow
RareamongAmericanactors,DepphasmadeanameforhimselfeffortlesslyswitchingbetweenmainstreamHollywoodmoviesandmore
随机试题
肾脏平片,肾轮廓能显示的原因是
下面白癜风最常见的类型是
有一“红参”药材,疑似伪品,送检,经鉴定,其横切面有多数点状维管束排成数个同心环,味稍甜后微苦,久嚼麻舌,它可能是()。
差额计算法与连环替代法的区别在于()上。
简述儿童绘画发展的图式期有哪些特征。
十八大报告指出,“初次分配和再分配都要兼顾效率和公平,再分配更注重效率。”()
警惕投资后遗症并非要________,而是要在投资的同时,努力用好投资,把握投资方向,提高投资效益,以投资带动消费。填入横线部分最恰当的一项是()。
青衿:读书人
在美国备案申报纳税的公司中有38家公司纯收入超过1亿美元,在所有税收报表上报道的国外来源总的应征税收入中,它们占了53%。在国外来源总的应征税收入中,有60%是来自10多个国家的200份纳税申报。如上面陈述为真,则下面哪个也一定正确?()
"Haveyougotsomeredeggs?""No,butI’vegot______."
最新回复
(
0
)