Microbiology
Assignment no. 4
1-How does commercial sterilization differ from sterilization procedures used in a hospital or laboratory?
2-Outline the steps in the production of cheese, and compare the production of hard and soft cheeses. Which bacteria seem to be most frequently used in the production of food? Propose an explanation for this.
3-Explain the effect of dumping untreated sewage into a pond on the eutrophication of the pond. The effect of sewage that has primary treatment? The effect of sewage that has secondary treatment? Contrast your previous answers with the effect of each type of sewage on a fast-moving river.
4-The following organisms have important roles as symbionts with plants and fungi; describe the symbiotic
relationship of each organism with its host: cyanobacteria, mycorrhizae, Rhizobium, and Frankia.
5-Why is the phosphorus cycle important?
6-Which of the following can affect human cells? Explain why.
a. penicillin
b. indinavir
c. erythromycin
d. polymyxin
7-A patient with streptococcal sore throat takes penicillin for 2 days of a prescribed 10-day regimen. Because he
feels better, he then saves the remaining penicillin for some other time. After 3 more days, he suffers a relapse
of the sore throat. Discuss the probable cause of the relapse.
8-Compare pathogenicity with virulence.
9-How are capsules and cell wall components related to pathogenicity? Give specific examples.
10-Explain whether each of the following examples is a food infection or intoxication. What is the probable
etiological agent in each case?
a. Eighty-two people in Louisiana developed diarrhea, nausea, headache, and fever from 4 hours to 2 days after
eating shrimp.
b. Two people in Vermont developed malaise, nausea, blurred vision, breathing difficulty, and numbness 3 to 6
hours after eating barracuda caught in Florida.
11-Differentiate the terms in each of the following pairs:
a. etiology and pathogenesis
b. infection and disease
c. communicable disease and non-communicable disease
12-Define symbiosis. Differentiate commensalism, mutualism, and parasitism, and give an example of each.
13-In some viruses, capsomeres function as enzymes as well as structural supports. Of what advantage is this to
the virus?
14-Briefly discuss the importance of lichens in nature. Briefly discuss the importance of algae in nature.
