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
34
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] 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://tihaiku.com/zcyy/3715622.html
相关试题推荐
Surfingissomethingpeopleoftengethookedonaftertryingitafewtimes.
Surfingissomethingpeopleoftengethookedonaftertryingitafewtimes.
TodayI’dliketotalkaboutwhathelpspeoplesuccessfullyintegrateintoa
TodayI’dliketotalkaboutwhathelpspeoplesuccessfullyintegrateintoa
TodayI’dliketotalkaboutwhathelpspeoplesuccessfullyintegrateintoa
TodayI’dliketotalkaboutwhathelpspeoplesuccessfullyintegrateintoa
TodayI’dliketotalkaboutwhathelpspeoplesuccessfullyintegrateintoa
Thearmywasseeminglyvictorious,butsincemanypeoplelosttheirlives,itwa
Howmanypeoplediedunderthelamivudinedrugtreatment?[br][originaltext]A
Howmanypeoplediedunderthelamivudinedrugtreatment?[br][originaltext]A
随机试题
态度的构成因素包括()A.认知 B.情感 C.意向 D.行为 E.价值
若函数f(x)在x=x0处取得极值,则下列结论成立的是( )。
法洛四联症四种畸形不包括A.主动脉骑跨 B.右心室肥厚 C.肺动脉狭窄 D
企业的核心目标是:()A.生存 B.发展 C.获利 D.扩大市场份额
患者一身面目俱黄,黄色鲜明,腹微满,口渴,小便不利,舌苔黄腻,脉沉数。治疗应选用
教学案例: (师)上课前一分钟,先请一学生在讲台上玩电子游戏(大屏幕展示给全班
A.硫黄 B.白鲜皮 C.秦皮 D.土茯苓 E.乌梅治疗梅毒,湿热疮毒,
A.嗜碱性中幼粒细胞B.早幼粒细胞C.小淋巴细胞D.中性中幼粒细胞E.嗜酸性中幼
由于考虑风险损失,许多投资人不愿把资金投向高风险的高新技术产业,这属于( )。
(2017年真题)2015年5月1日,秦某与甲房地产开发公司(以下称甲公司)签订
最新回复
(
0
)