Compare and contrast the streak-plate method of isolation with the pour-plate method of isolation
What will be an ideal response?
The streak-plate and the pour-plate methods of bacterial isolation are both used to produce pure cultures of bacteria from specimens. Both techniques involve the use of agar-based growth media contained in Petri plates. Additionally, both techniques involve the use of dilutions as a means of isolating single cells or groups of cells that then grow into isolated colonies. However, there are several significant differences between the two techniques. The main difference is the way in which the specimen is diluted. In the streak-plate method, the specimen is diluted by use of an inoculating loop that spreads organisms over the surface of the agar. Thus, colonies appear only on the agar surface. In the pour-plate method, however, dilutions of the specimen are made in tubes of broth and then each dilution is added to melted agar, which is then poured into Petri dishes. Thus, microbes are mixed throughout the agar, and colonies will appear both in and on the medium.
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Standard pasteurization methods are used to
A) reduce microbes that cause spoilage. B) remove all thermoduric microbes. C) reduce microbes that cause disease. D) remove all microbes. E) reduce microbes that cause disease or spoilage.
The prevalence rate of tuberculosis in one particular county in Texas is 7/1000 people, while the incidence rate for 2011 is 2/1000 people. Analyze this data and summarize the situation.
A. Incidence rate should really be higher than prevalence rate because it includes all new cases for the year. B. The data were collected incorrectly because the two values should match. C. Prevalence rate is higher than incidence rate because the number of people still alive with tuberculosis is higher because of better treatments. D. Prevalence rate and incidence rate cannot be determined for the same disease.
Which structure surrounds and protects the brain in all vertebrates?
a. pharynx b. neural crest c. oral hood d. notochord e. cranium
The value of inserting human genes suspected of
causing Alzheimer disease into mice is to a. make mice act more human. b. make antibodies, which can be injected into suffering patients. c. develop mice that can serve as models for study of this condition. d. use the mice for production of a vaccine for the disease. e. accomplish all of these.