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
2016-01-14
54
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 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.
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.
选项
答案
细菌置于生长皿中时,它们必须要适应新环境,在这一适应过程中,它们的生长过程缓慢。
解析
(将被动化为主动,在适当的地方增加词语,如growth译为“它们的生长”。)
转载请注明原文地址:https://jikaoti.com/ti/RCtMFFFM
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
Thegraphbelowshowtheincreaseofthepeople’sincomeandpeople’ssavingsinChina.Writeareporttodescribetheinformati
YourpassportisyourofficialidentificationasanAmericancitizen.InAmerica,mostpeopleneverconsiderobtainingapasspor
Whichofthewords,AtoD,ismissingfromthebrackets?BEND(LOOPHOLE)LAIRHALT(……)LEAF
Iwishyou’dmetmyUncleBill.Hewasatallman--sotallthathecouldchangethebulbsinlightsocketswhilehardlyreaching
IfHarrydidnotattendtheconferencelastnight,He______toomuchworktodo.
Whenwasthelasttimeyousawafrog?Chancesare,ifyouliveinacity,youhavenotseenoneforsometime.Eveninwetarea
OneofAmerica’smostimportantexportsishermodernmusic.Americanpopularmusicisplayingallovertheworld.Itisenjoyed
旅游业是全世界最大的雇主,全球10%的工作岗位都是由旅游业创造的。(accountfor)
【T1】我希望这个新学年成为对我的学生们有益的一年。(want…tobe)他们会在新学年学习很多东西,包括微积分、莎士比亚和失败。没错,就是失败。根据多种流传的说法,梭罗是个失败者。这位哈佛毕业生似乎把自己的大部分时间都用来在瓦尔登湖畔家
YYZZZYZZYisto221112112asYYZZYZZYisto______.
随机试题
行车中发现左侧轮胎漏气时怎样处置?
《银行业从业人员职业操守》规定的银行业从业人员不包括()
关于代扣代缴、代收代缴税款账簿,下列说法中正确的是()。
企业在销售收入确认之后发生的销售折让(不属于资产负债表日后事项),应冲减确认收入期闸的收入。()
经()批准,可以查询从事生产、经营的纳税人、扣缴义务人在银行或者其他金融机构的存款账户。
()对于湿地相当于稀土对于()
设曲线y=在(x0,y0)处有公切线(如图3—7所示),求这两曲线与x轴围成的平面图形绕x轴旋转而成的旋转体的体积V。
A、 B、 C、 D、 D
Morepeopledieoftuberculosis(结核病)thanofanyotherdiseasecausedbyasingleagent.Thishasprobablybeenthecaseinquit
【S1】【S9】
最新回复
(
0
)