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
49
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.
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/hgAK777K
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
(89)IwashesitanttowritethisarticlethewayIhavebecauseIknowsomepeoplemaymisinterpretmyintentions,soIwillcl
Ifthereisanysingle【21】thatmakesforsuccessinliving,itistheabilitytoprofitbydefeat.EverysuccessIknowhasbeen
Everyyearalargenumberofyoungpeopleleaveschoolandbeginwork.Some【21】jobsonfarmsorinindustry.Othersacceptposit
TeadrinkingwascommoninChinafornearlyonethousandyearsbeforeanyoneinEuropehadeverheardabouttea.【74】,mainlybec
Normallyastudentmustattendacertainnumberofcoursesinordertograduate,andeachcoursewhichheattendsgiveshimacr
Thesetwosummermonthsadduptogiveamonthinspringifyounumbercarefullytosubstituteforeachoftheletters.Whatis
Makingagoodfirstimpressionisimportantforbuildingrelationshipswithotherpeople.Inbusinessnetworking,apositivefir
【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
YYZZZYZZYisto221112112asYYZZYZZYisto______.
YYZZZYZZYisto221112112asYYZZYZZYisto______.
随机试题
何谓兴奋一收缩耦联?
乳腺癌的好发部位是
患者男,28岁。两年前体检查出HBsAg阳性,身体无任何不适,平素体健,近一周来厌食恶心,巩膜黄染,实验室检查:ALT300U/L,血清总胆红素150μmol/L,HAVIgG抗体(﹢),HBsAg(﹢),HBeAg(﹢),抗HBcIgM抗体(﹢)。
企业劳动争议调解委员会的组成包括()。
“今明主在上,群臣将顺之不暇,毋用多言!诸君不见立仗马乎?食三品料,一鸣辄斥去,悔之何及!”这段话描述的是()专权。
下列关于OSPF协议的描述中,正确的是()。
窗体上有单选钮和列表框控件。单击名称为Option1、标题为"国家"的单选钮,向列表框中添加国家名称,如下图所示。Option1的单击事件过程如下:PrivateSubOption1_Click() Dimarr arr=Array("
下列叙述中正确的是( )。
()明码标价()信息技术()商品目录()房屋出租
网上购物(onlineshopping)是中国近几年日益流行的新型购物方式。人们在购物网站搜索自己想要的物品,在网上发出电子订单并付款。卖家则通过快递公司送货上门。网上购物的主要人群最初是大学生和白领,现在大多数的网民(netizen)都有过网购的经历。
最新回复
(
0
)