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
32
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.
Bacteria are also critical to many industrial processes, from fermenting wine to recycling wastes.
选项
A、TRUE
B、FALSE
答案
A
解析
(对很多工业流程,例如葡萄酒酿造和工业废料再循环来说,细菌是至关重要的因素。)
转载请注明原文地址:https://kaotiyun.com/show/LZAK777K
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
Normallyastudentmustattendacertainnumberofcoursesinordertograduate,andeachcoursewhichheattendsgiveshimacr
A、Itisapitythatthewomanfailedtocometotheparty.B、Thewomandidnotlikethepartyatall.C、Themanhimselfdidn’ts
Readthefollowingadvertisementandwritealetterofapplicationof120words.Donotwriteyouraddressorname.WANTEDFA
What’sTania’sphonenumber?
ThefourthcomponentoftheSwedishsocialsystemisthatitspoliciesensurefullemploymentandincreasethemobilityoflabou
ThefourthcomponentoftheSwedishsocialsystemisthatitspoliciesensurefullemploymentandincreasethemobilityoflabou
______,amanwhoexpresseshimselfeffectivelyissuretosucceedmorerapidlythanamanwhosecommandoflanguageispoor.
Renaissancewastherevivalofclassical______inEuropeanhistory.
Iftwotypistscantypetwopagesintwominutes,howmanytypistswillittaketotype18pagesinsixminutes?
(81)具体说,信息化主要是反映在沟通手段的网络化,也就是所谓的网络经济。这网络就是指由卫星、光纤、电缆和电话线路把世界各个角落联系到一起的电脑网络。(82)只要用鼠标一点,在地球另一端的信息马上就会以每秒钟绕地球七周半的光速跑到你的电脑荧光屏上。
随机试题
正火比退火的生产周期短、成本低,且操作方便,故在可能的情况下优先采用正火。()
“走出去”战略与______共同构成了我国对外开放的完整格局。
下列施工阶段的目标控制工作中,属于监理工程师质量目标控制工作的有()
垂直于坝轴线方向的缝称为()。
为提高计算机的安全性,密码应尽可能做到()。
债券发行人通过发行债券筹集的资金一般没有期限,债权人随时可以取回本金和合同约定的利息。()
小明平时易受暗示,屈从权威,喜欢按照他人的意见办事,不善于应付紧急情况,他的这种性格类型属于()。
根据下列材料,回答问题。材料1深圳建市25年来,曾用18年使CDP达到1000亿元,5年后达到2000亿元,而突破3000亿元仅用了2年。25年来,深圳年均增长速度近30%,生产总值增加了1800倍,人口从30万增长到1000万。人
(1)用SQL语句完成下列操作:检索“田亮”所借图书的书名、作者和价格,结果按价格降序存人book_temp表中。(2)在考生文件夹下有一个名为menu_lin的下拉式菜单,请设计一个名为form_menu的顶层表单,将菜单menu_lin加入到
下面属于系统软件的是()。
最新回复
(
0
)