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
2023-10-16
80
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℃ 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. [br] Most bacteria used in medicine and industry grow best between the temperature of 20 °F and 45°F.
选项
A、TRUE
B、FALSE
答案
B
解析
(文章第三段最后一句话明确指出Most bacteria used in medicine and industry grow best between 20℃and 45℃。)
转载请注明原文地址:http://tihaiku.com/zcyy/3101522.html
相关试题推荐
Everyyearalargenumberofyoungpeopleleaveschoolandbeginwork.Some【
Everyyearalargenumberofyoungpeopleleaveschoolandbeginwork.Some【
Everyyearalargenumberofyoungpeopleleaveschoolandbeginwork.Some【
Everyyearalargenumberofyoungpeopleleaveschoolandbeginwork.Some【
Everyyearalargenumberofyoungpeopleleaveschoolandbeginwork.Some【
PeoplelivingonpartsofthesouthcoastofEnglandfaceaseriousproblem.
PeoplelivingonpartsofthesouthcoastofEnglandfaceaseriousproblem.
PeoplelivingonpartsofthesouthcoastofEnglandfaceaseriousproblem.
Whatarethemanandwomantalkingabout?[br][originaltext]M:Manypeoplesee
Whatarethemanandwomantalkingabout?[br][originaltext]M:Manypeoplesee
随机试题
Ioncefoundoutthatdoingafavorforsomeonecouldgetyouintotrouble.
Toerrishumanandtoforgivedivine,accordingtotheoldadage.Humanswh
以下属于跨期套利的是()。[2009年9月真题]A、卖出A期货交易所4月锌期货合约,同时买入A期货交易所6月锌期货合约B、卖出A期货交易所5月大
某研究者在用心理物理法测量感觉阈限时,若他想在测量时,让被试亲自参与,并且更有效
在事业部制的组织架构下,子公司销售部一般称为一级利润中心。()
直角刚杆OAB在图示瞬间角速度ω=2rad/s,角加速度ε=5rad/s2,若O
下列症状可能与绝经有关,但除外A.尿频尿急 B.肢体疼痛 C.易于激动 D
教学《兰亭集序》时,教师列举其他文章,引导学生进一步体会骈文特点,下列作品适合的
购进材料款未付时,这笔未结算的款项应确认为()。A.负债 B.资产 C.收入
既能凉血止血,又能清热安胎、利尿解毒,善治胎动不安、湿热淋痛的药物是A.小蓟
最新回复
(
0
)