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
2013-11-20
45
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.
Most people consider bacteria dangerous: actually, most of them are beneficial to humans.
选项
A、TRUE
B、FALSE
答案
A
解析
(文章第一段指出大多数人认为细菌是危险的,但事实上只有一小部分的细菌会致病,而大多数的细菌对人体是有益的。)
转载请注明原文地址:https://kaotiyun.com/show/LgAK777K
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
Ifthereisanysingle【21】thatmakesforsuccessinliving,itistheabilitytoprofitbydefeat.EverysuccessIknowhasbeen
Ifthereisanysingle【21】thatmakesforsuccessinliving,itistheabilitytoprofitbydefeat.EverysuccessIknowhasbeen
TeadrinkingwascommoninChinafornearlyonethousandyearsbeforeanyoneinEuropehadeverheardabouttea.【74】,mainlybec
Whichofthebottomwatchescompletesthesequence?
Distributetheremainingnumbers1-7and9-12aroundthenodessothateachofthesixlinesoffournumbersaddupto26.
有人建议,中国所有的博物馆都应对中小学生免费开放,使他们有更多机会获得广博的知识。(access)
【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
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
RareamongAmericanactors,DepphasmadeanameforhimselfeffortlesslyswitchingbetweenmainstreamHollywoodmoviesandmore
【T1】人民很容易陷入这样的思维,觉得一旦把东西扔掉,他就消失了。(getstuckin)针对这样的想法,某机构固体废弃物及再循环部门经理表示:“什么都没有消失"。刚刚扔进垃圾桶的塑料瓶也许离开了我们的视线,但并不意味着它们就消失了。我们往往认为:眼不
随机试题
简述实施网络财务的重要意义。
企业由于将资金投放占用于应收账款而放弃的投资于其他方面的收益是()
患者,女性,30岁。近5个月来自觉乏力,怕热多汗,并出现食欲增强,体重减轻,大便次数增多,每日3~5次,不成形。查体:Bpl45/68mmHg,皮肤潮湿,手颤,甲状腺Ⅱ度肿大。对诊断最有帮助的检查是
阵发性室上性心动过速并发变异型心绞痛,宜采用的治疗药物是()
确诊二尖瓣狭窄最可靠的辅助检查是
混凝土拆模申请单由施工单位填写,报()审批。
二氧化碳对人体有窒息作用,当含量达到()以上时能使人窒息死亡,因此二氧化碳灭火系统的使用受到局限。
关于价格水平、总供给和总需求之间的关系,下列说法中错误的是()。
2013年4月,某市税务机关在对甲公司2013年度的纳税情况依法进行税务检查时,发现甲公司有逃避纳税义务的行为,并有明显的转移、隐匿应纳税收入的迹象。税务机关责令甲公司于2013年4月11日至4月20日限期补税,但甲公司在4月20日期限届满后,仍拒绝补税。
国家扶持动漫产业的决心和力度是_________的,动漫产业的发展也是__________的,但关键是“政策扶持”不应成为“政策导向”,动漫产业的健康发展的最终还要依赖于市场的认可。依次填入划横线部分最恰当的一项是()。
最新回复
(
0
)