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
51
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
Manyayoungpersontellsmehewantstobeawriter.Ialwaysencouragesuchpeople,butIalsoexplainthatthere’sabigdiff
Welcometo"SoftwareWorld"—bringingyoutheverylatestinformationonwhatiscurrentlyavailableonCD-ROM.Areyouadirec
Welcometo"SoftwareWorld"—bringingyoutheverylatestinformationonwhatiscurrentlyavailableonCD-ROM.Areyouadirec
Onetheoryabouttheuniversesaysthatithasnoboundary,noedge.ThistheorywasproposedbyStephenHawkingandJimHartle.
Howmanyminutesisitbefore12atnoonif90minutesagoitwasfourtimesasmanyminutespast9a.m.?
如果你是一个中等水平的读者,你能够以每分钟300字的速度阅读一本中等水平的书。不过,你必须每天这样坚持下去,否则就无法保持这种水平。【T1】你也不可能以这个速度阅读科学、数学、农业、商业方面的书,或是对你来说内容生疏的书。(Nor…or…)你绝不会以这种速
中国经济发展潜力大、优势足、空间广,前景光明。【T1】我们有9亿多劳动力,其中1.7亿多受过高等教育或有专业技能。(非限制性定语从句)每年大学毕业生700多万,中职毕业生500多万。【T2】科技人员数量世界第一,研发投入(R&Dinput)世界第
Forthispart,youareallowed30minutestowriteashortessay.Youshouldstartyouressaywithabriefdescriptionofthepic
A、TovisitWalconElectronicsforfuturecooperation.B、Toprepareforaworldwidebusinessexposition.C、Tosignabigcontract
曾报道过的全球医生会诊,网上外科手术和通过网络协作科研,就是这种高层次网络化的先例。(earlyexample)
随机试题
功用为解肌透疹的方剂是功用为解肌清热的方剂是
选择性作用于βl受体的药物是
我国已将()种职业致癌物所致的癌症,列人职业病目录。
甲市某县电力调度大楼,层数四层,耐火等级不低于()级。
集合计划终止之日起一个工作日内,管理人和托管人应当在扣除管理费、托管费等费用后,将集合计划资产按照委托人持有集合计划份额的比例或集合资产管理合同的约定,以证券形式分派给委托人。( )
甲公司2012年1月1日购入面值为200万元,年利率为4%的A债券;取得时支付价款208万元(含已到付息期但尚未发放的利息8万元),另支付交易费用1万元,甲公司将该项金融资产划分为交易性金融资产。2012年1月5日,收到购买时价款中所含的利息8万元,201
甲公司有一注册商标,其有效期将于1997年6月1日届满,该公司需要继续使用此商标,便向乙律师提出咨询。乙律师的意见正确的有()
因为面临预算困难,政府机构减少了他们的科研基金,更大量的类似的研究现在由私人基金赞助。这种变化意味着可能导致具有争论性后果的研究将占据所有被资助项目的较小比例。因为私人基金考虑到他们的公众形象,倾向于避免争议。下列哪一个是上文所做的假设?
①导游_______地告诉我们,遇到野象没什么,最多回头跑50米,野象就不会再追了。②你为什么不对我说真话?你为什么老是_______,应付我?③他们看我们,也许就像我们看蚂蚁一般,即使我们中间的那么伟大人物,在他们看来也_______
Thebossmadetheworkers(work)______frommorningtillnight.
最新回复
(
0
)