首页
登录
职称英语
Most people consider bacteria dangerous. After all, these microorganisms cau
Most people consider bacteria dangerous. After all, these microorganisms cau
游客
2024-08-11
14
管理
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. [br] 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://tihaiku.com/zcyy/3715620.html
相关试题推荐
______feltthatsocietyforcedtoomanyrulesonpeopleandkeptthemfromlivin
______untilrecently,peoplewhoareleft-handedhavebeenconsideredabnormal.A
Faith;Howmanypeopledoyouthinkwillshowupfordinner?Louis;Onlytwoof
Forsomepeople,itmaybe______torememberwhattheyhavejustread______recal
Inthispartoftown,peopleareonlyworriedaboutkeepingupwith______.A、the
Atthebeginningofthe20thcentury,peoplemadecoffee______aclothbagfullo
The______driverthinksthataccidentsonlyhappentootherpeople.A、generalB、us
Youngpeopletodayseemunabletopartwithsmartphones,laptopsandiPads.The
Internationaltravelisbecomingeasier,fasterandcheaperformanypeoplenowa
Somepeoplethinkthateachagehasitsownartform.Thereforethetraditional
随机试题
One-thirdoftheworld’snearly700millionchildrenunderfiveyearsoldare
Fewpleasurescanequalsuchofacookdrinkonahotday.A、thisB、allthisC、th
双层实木地板楼面的隔声层位于()。 A.结构层与找平层之间 B.双层地
糖皮质激素治疗支气管哮喘的主要目的是A.解除支气管痉挛 B.减少分泌物的产生
请按所提供的教材片段,设计1课时的教学简案(也可以是单元中的一课)。 要求:
《义务教育数学课程标准(2011年版)》指出:“模型思想的建立是学生体会和理解数
患儿女,7岁。因风湿热入院,目前使用青霉素和阿司匹林治疗。近日该患儿出现食欲下降
简述现代企业人力资源管理各个历史发展阶段的特点。
韦克斯勒认为,智力发展的最高峰应在( )A.18~22岁 B.22~25岁
下列不属于天王补心丸药物组成的是A.天冬、麦冬 B.酸枣仁、柏子仁 C.茯苓
最新回复
(
0
)