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Microbiology Study Questions

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1. Clostridium and Streptococcus are both catalase-negative. Streptococcus grows by fermentation. Why is Clostridium killed by oxygen, whereas Streptococcus is not?

2. Assume that after washing your hands, you leave ten bacteria cells on a new bar of soap. You then decide to do a plate count of the soap after it was left in the soap dish for 24 hours. You dilute 1g of the soap 1:106 and plate it on standard plate count agar. After 24 hours of incubation, there are 168 colonies. How many bacteria were on the soap? How did they get there?

3. Why is each of the following bacteria often resistant to disinfectants?
1. Mycobacterium
2. Pseudomonas
3. Bacillus

4. Explain why gram-negative bacteria are more resistant to biocides than gram-positive bacteria. Be specific and descriptive in your response. A description of the differences between gram-negative and gram-positive bacteria should be included, along with an explanation of why any of those differences would have anything to do with the actions of biocides.

5. Ciprofloxacin, erythromycin, and acyclovir are used to treat microbial infections. Ciprofloxacin inhibits DNA gyrase. Erythromycin binds in front of the A site on the 50S subunit of a ribosome. Acyclovir is a guanine analog.
1. What steps in protein synthesis are inhibited by each drug?
2. Which drug is more effective against bacteria? Why?
3. Which drug is more effective against viruses? Why?
4. Which drugs will have effects on the host's cells? Why?
5. Use the index to identify the disease for which acyclovir is used. Why is it more effective than erythromycin for treating this disease?

6. Design an experiment using the vaccinia virus to make a vaccine against AIDS virus (HIV).

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Here is a brief summary:

Clostridium and Streptococcus are both bacteria. The are important microorganisms due to their medical aspect. They cause disease in humans and are quite pathogenic.

Clostridium is a strain of bacteria classified as anaerobic. Anaerobic organisms thrive in environments devoid of oxygen. More specifically Clostridium is an obligate anaerobe. This means that when they are exposed to oxygen they will die. Instead of breathing clostridium bacteria sustain themselves by fermentation, a chemical process that converts lactic acid into energy. Streptococcus also creates energy by fermentation, but they are facultative anaerobes. They can also use oxygen for energy when available.

3.Why is each of the following bacteria often resistant to disinfectants?
1.Mycobacterium
2.Pseudomonas
3.Bacillus

Following bacteria are often resistant to disinfectants because:
1. Mycobacterium-
Mycobacterium tuberculosis is resistant to disinfectants particularly because the waxy outer coating and complex cell wall of mycobacteria prevents the penetration of various chemical antibacterials. The extra-slow growth rates of these bacteria may also give rise to their reduced susceptibility since disinfectants typically are more effective against actively growing bacteria than against not-growing bacteria.

2. Pseudomonas-
Pseudomonas have the ability to metabolise a variety of diverse nutrients. Combined with the ability to form biofilms, they are thus able to survive in a variety of unexpected places. The ability to thrive in harsh conditions is a result of their hardy cell wall that contains porins. Their resistance to most antibiotics is attributed to efflux pumps called ABC transporters, which pump out some antibiotics before they are able to act and the permeabiliity barrier afforded by its outer membrane LPS. Also, its tendency to colonize surfaces in a biofilm form makes the cells impervious to therapeutic concentrations antibiotics. Moreover, Pseudomonas maintains antibiotic resistance plasmids, both R-factors and RTFs, and it is able to transfer these genes my means of the bacterial processes of transduction and conjugation.

3. Bacillus-
Bacillus forms spores and spores are resistant to many disinfectants. Bacterial spores of the genera Bacillus have been widely studied and are invariably the most resistant of all types of bacteria to antiseptics and disinfectants. The coat(s) and cortex of the spores are associated to the mechanism(s) of resistance presented by bacterial spores to antiseptics and disinfectants. In case of ...

Solution Summary

Clostridium and Streptococcus are both bacteria. The are important microorganisms due to their medical aspect. They cause disease in humans and are quite pathogenic.

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Microbiology Questions

Please help with the attached micro questions. Several questions have not been answered as I cannot find anything referring to the topic in my text.

1. Passive immunity can
a. Involved an injection of antibodies
b. Be acquired by a child from its mother
c. Be administered with a convalescent serum
d. All the above are correct

6. In the secondary anamnestic response
a. The booster injection stimulates an immediate antibody response
b. Phagocytosis is stimulated by lymphokines
c. The body is exposed to antibodies
d. Polyvalent serum is injected to the body

7. An example of a second generation vaccine is that for
a. Measles, mumps and rubella
b. Polio
c. Diphtheria and tetanus
d. Streptococcal pneumonia

8. Antibodies produced against bacterial pili would inhibit
a. Capsular polysaccharide production
b. Penetration of bacteria through human tissues
c. Bacterial motion
d. Attachment of bacteria to human tissue

11. When the immune system recognizes a foreign protein in a serum injection and complement is activated, a person may develop a type of allergy called
a. Immune complex disease
b. Anaphylaxis
c. Hypersensitivity
d. Serum Sickness

15. Innate immunity is the same as
a. Natural passive immunity
b. Acquired active immunity
c. Nonspecific defense
d. Specific immunity

23. The antigenic substance that sets off an anaphylactic reaction
a. Interacts with the body's T-Lymphocytes
b. Is known as an allergen
c. Induces smooth muscle contraction directly
d. Contains cyclic AMP molecules

28. The major histocompatibility genes encode
a. The individual's blood type
b. The development of the Rh antigen
c. A series of cell-surface antigens
d. The mediators that develop in anaphylaxis

30. If a woman with blood type A+ has a child by a man whose blood type is A-
a. The child will have type B blood
b. Hemolytic disease will occur in the second child to be conceived
c. The child will not suffer from hemolytic disease nor will a future child
d. The woman will develop Rh antibodies at the conclusion of pregnancy

34. In a blood transfusion, the
a. Recipient should not contain antibodies to the donor's antigens
b. Recipient should not contain antigens to the donor's antibodies
c. Recipient should not contain antigens or antibodies cross-reactive to the donor's
d. All the above are correct

43. The indicator system in the complement fixation test is used to determine whether complement was used up in the test system
a. True
b. False

45. In the preparation of toxoids, the antigenicity of the toxin remains while the toxigenicity is destroyed
a. True
b. False

47. The application of the ELISA test is in the AIDS test for the detection of HIV antigens.
a. True
b. False

48. Immunizing agents include toxoids, subunit vaccines containing parts of microorganisms, and synthetic vaccines such as that used for hepatitis B
a. True
b. False

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