Biology 325: Tutor-Marked Exercise 3

This assignment is made up of ten questions, each of which is worth ten marks. Your mark for this exercise will comprise 10% of your final grade for the course. You should complete TME 3 after you have completed Unit 12 of the course. This assignment may be submitted online via the appropriate Assignment Drop Box. If you choose to send it by post mail, please include a TME Form, which you can access atmyAU or at your course website.

  1. Column A lists terms related to viruses, viroids, and prions. Column B lists definitions for these terms. For each term listed in Column A, select the best answer from Column B.

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31

Column A

capsid

complex virus

retrovirus

viroid

T2 bacteriophage

transformation

adenovirus

prion

lysogenic cycle

helical virus

Column B

  1. contains a head and a tail
  2. ssRNA virus
  3. tumour cells undergo this process
  4. viral protein coat
  5. latent state
  6. poxvirus
  7. oncovirus
  8. small, naked pieces of RNA
  9. polyhedral virus
  10. kuru-causing agent

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31

  1. The following questions pertain to viruses and infectivity:
  1. Draw and label clearly the basic structures of a retrovirus, a filovirus, and a coronavirus.
  2. A scientist wanted to test the infectivity of two new bacteriophages (phages) on a strain of E. coli. In doing so, the scientist mixed a sample of the organisms together with each phage and distributed the samples in molten agar after incubating the mixtures for a period of up to three hours. Table 1 describes the results obtained.

Table 1. Infectivity of phage A and phage B on E. coli
over time, represented in plaque-forming units per ml.

Time (hours) / Phage A (pfu/ml) / Phage B (pfu/ml)
1 / 40 / 2
2 / 120 / 30
3 / 300 / 40
  1. Draw a clearly labelled and titled graph comparing each sample for each time point given.
  2. Compare the effectiveness of each of the phages used.
  3. Explain why scientists use phages in their research studies.
  1. A patient was admitted to hospital with a high fever (40C), a headache, and diarrhea. He informed the doctor that he had returned from travelling abroad two weeks ago. Microbiological examinations indicated that the patient was infected with a species of Salmonella. During the course of hospitalization, the patient was treated with a quinalone antibiotic and the numbers of organisms in the blood were monitored. The graph below shows the infectivity curve. The values shown on this curve are the numbers of organisms/ml over the course of the illness.

Figure 1. Bacterial load of hospitalized patient over the period of infection.
  1. Use your knowledge of the disease process, the epidemiology, and the information provided above to describe the stages of this disease.
  2. Identify the disease in this case and the causative agent. Suggest the possible source of this infection and how this illness could have been prevented.
  1. Column A lists terms related to epidemiology and diseases. Column B lists descriptions and definitions. For each term listed in Column A, select the best answer from Column B. Please note that the options listed in Column B can be used once, more than once, or not at all.

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31

Column A

pandemic disease

septicemia

nosocomial infection

prodromal period

acute disease

epidemic disease

pathology of disease

incidence

etiology of disease

Column B

  1. early symptoms of infection
  2. symptoms
  3. world-wide effects
  4. cause of disease
  5. afflicts large numbers of people
  6. causes fever
  7. human reservoir of infection
  8. infection that lasts for a brief period
  9. hospital-acquired
  10. number of people infected during a particular time period

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31

  1. Foot-and-mouth disease (FMD) is a life-threatening disease of unvaccinated livestock. In a study of this disease, unvaccinated cows were treated with one of five concentrations of viral particle in suspension. Each treatment was administered to twenty cows; ten received a liquid suspension injected into the tongue, and another ten received an aerosol suspension. The results of this study are summarized in Table 2.
Table 2.Number of infected cows following injection or aerosol administration of Foot-and-Mouth Disease Virus (FMDV).
Concentration
(viral particles/ml) / Number of cows
infected by injection / Number of cows
infected by aerosol
0 / 0 / 0
103 / 2 / 0
104 / 5 / 1
105 / 7 / 3
106 / 10 / 5
  1. Describe the virulence of this organism by expressing the infectious dose of each procedure.
  1. Compare the results of the two experimental procedures.
  2. What procedures would the researchers use to test the lethal dose of these organisms?
  3. Describe an experiment to text the effects of vaccination on a different cattle group.

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31

  1. Answer the following questions that pertain to innate immunity.
  1. Identify one physical factor and one chemical factor that prevent microbes from entering the body through the skin, and describe how prevention of invasion is achieved.
  1. Define commensalism and give two examples of organisms that are commensals to the human body.
  2. Briefly explain how the body removes bacteria at a site of injury.
  1. Answer the following questions regarding adaptive immunity.
  1. Draw a diagram of a typical antibody molecule, and indicate the following: heavy chain, light chain, Fc region, variable region, and antigen binding site.
  1. Illustrate and explain how a virus-infected cell is killed by a cytotoxic T lymphocyte.
  1. Column A lists terms related to immunology. Column B lists components that describe immunological events. For each of the terms listed in Column A, select the best answer from Column B. Please note that the options listed in Column B can be used once, more than once, or not at all.

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31

Column A

epitope

helper T cell

complement

MHC molecule

immunoglobulin

B cell

T cell receptor

cytokine

natural killer cell

hapten

Column B

  1. antibody
  2. small organic molecule
  3. non-specific component of defense that causes cytolysis
  4. antigenic determinant
  5. results in the membrane attack complex (MAC)
  6. secretes cytokines
  7. involved in antigen presentation
  8. binds antigen presented by an MHC molecule
  9. plasma cell
  10. interferon

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31

  1. A school-age child developed severe respiratory symptoms and went into shock following the ingestion of a peanut. The child’s first exposure to peanuts took place without incident, but on this subsequent exposure, he suffered these symptoms and required immediate action by paramedics. Now this child must be very careful not to come in contact with any source of peanuts. Considering this information, answer the following questions:
  1. What is the name of the immunological reaction that occurred in this child?
  1. Describe the steps of immunological events that resulted in these symptoms.
  2. Identify the immune cells that predominated during this event.
  3. What primary intervention would the paramedics have taken?
  4. Why must this child avoid contact with peanuts?
  1. Infection by the HIV virus and the resulting disease, AIDS, is an example of an immunodeficiency.
  1. What does the term immunodeficiency mean? Is AIDS acquired or congenital? Explain.
  1. Describe the process of infection by HIV with respect to viral-host cell interactions.
  2. What immune functions are compromised by this infection?
  3. List three infections that can occur as a result of this disease, and list the symptoms.
  4. Explain why HIV is capable of evading the immune response.

Biology 325: Introductory Microbiology Tutor-Marked Exercise 31