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
35
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://jikaoti.com/ti/y7tMFFFM
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
Simon:I’mareporterfromtheHendonStandard.______Celia:Yes,IwasstandingattheendofElmAvenue,bythepark.Simon:
PopstarstodayenjoyastyleoflivingwhichwasoncetheprerogativeonlyofRoyalty.Wherevertheygo,peopleturnoutinthe
PopstarstodayenjoyastyleoflivingwhichwasoncetheprerogativeonlyofRoyalty.Wherevertheygo,peopleturnoutinthe
Thewritersofmurderstoriesgotoagreatdealoftroubletokeepusguessingrightuptotheend.Inactualfact,peopleofte
Manyayoungpersontellsmehewantstobeawriter.Ialwaysencouragesuchpeople,butIalsoexplainthatthere’sabigdiff
ThefourthcomponentoftheSwedishsocialsystemisthatitspoliciesensurefullemploymentandincreasethemobilityoflabou
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
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
AlthoughFrench,German,AmericanandBritishpioneershaveallbeencreditedwiththeinventionofcinema,theBritishandthe
随机试题
试述《伪君子》中答丢夫形象的概括意义。
患者,男性,44岁。2年前诊断慢性肾功能衰竭。1月前出现进餐后上腹饱胀、恶心、呕吐,加重2天入院。查体:尿量减少,内生肌酐清除率20ml/min。目前正确的饮食方案是
某工程项目双代号网络计划如下图所示,则该网络实施优化能够达到最短工期为()天。
下列符合登记会计账簿基本要求的是()。
凭证式国债承销团成员原则上不超过()家。
下列各项目中,应当确认为收入的有()。
当安全风险提示级别为一级的,则特别严重,用橙色标示。()
根据资料,回答以下问题。2009年全国海洋生产总值31964亿元,比上年增长8.6%。全国海洋生产总值占国内生产总值的9.53%,占沿海地区生产总值的15.5%。海洋第一产业增加值1879亿元,海洋第二产业增加值15062亿元。海洋第三产业增加值1502
甲、乙二人协商共同投资,甲从乙处取了15000元,并以两人名义进行了25000元的投资,但由于决策失误,只收回10000元。甲由于过失在己,愿意主动承担的损失。问收回的投资中,乙将分得多少钱?()
系统开发中的详细设计包括Ⅰ.代码设Ⅱ.逻辑设计Ⅲ‘输入输出设计Ⅳ.模块结构与功能设计Ⅴ.程序设计Ⅵ.数据库文件设计
最新回复
(
0
)