MIC 205A Dr. Jan Decker
Exam 1 KEY
September 15, 2006
Part 1 MULTIPLE CHOICE: Read each question and the answers carefully. Pick the one BEST answer and darken the corresponding letter on the scantron. Each answer is worth 3 points, for a Part one total of 90 points.
1. ______________ is/are found in the cytoplasm of eukaryotic but not prokaryotic cells.
- a. Chromosomes
- b. Lysosomes
- c. Pili
- d. Ribosomes
2. (WHITE) The organism in this micrograph is approximately 1-2 micrometers in length; therefore, it is probably a
- a. bacterium.
- b. helminth parasite.
- c. virus.
- d. Can’t tell from this information.
3. (WHITE) The hair-like structures surrounding this microbe are for
- a. attachment to surfaces.
- b. maintaining the cell shape.
- c. protection from white blood cells.
- d. survival in harsh environments.
2. (YELLOW) The organism in this micrograph [only (a) was shown] is approximately 10-12 micrometers in length. Therefore, it is probably a
- a. bacterium
- b. helminth parasite.
- c. protozoan parasite.
- d. Can't tell from this information.
3. (YELLOW) The long 'tails' on this microbe are probably for
- a. attachment to surfaces.
- b. motility.
- c. protection from white blood cells.
- d. survival in harsh environments.
2. (GREEN) The organism in this micrograph is approximately 100 nanometers in length; therefore, it is probably a
- a. bacterium.
- b. helminth parasite.
- c. virus.
- d. Can't tell from this information.
3. (GREEN) The short structures surrounding this microbe are for
- a. attachment to host cells.
- b. maintaining the microbe's shape.
- c. protection from white blood cells.
- d. survival in harsh environments.
4. Which of the following is NOT TRUE of peptidoglycan?
- a. Peptidoglycan is composed primarily of sugars cross-linked with short chains of amino acids.
- b. Peptidoglycan is found in Gram positive but not Gram negative cell walls.
- c. Peptidoglycan is the principal component of prokaryotic cell walls.
- d. Peptidoglycan cross-linking gives bacterial cells their characteristic shapes.
5. Plasmodium falciparum causes
- a. diarrhea.
- b. malaria.
- c. skin infections.
- d. Valley Fever.
6. Archaea
- a. are easily cultured in the laboratory.
- b. are eukaryotes.
- c. have peptidoglycan cell walls.
- d. often live under extreme conditions.
7. From its name you can tell that Streptococcus pyogenes is an example of a
- a. protozoan parasite.
- b. rod-shaped bacterium.
- c. round bacterium in chains.
- d. virus.
8. The cytopathic effect of a virus is its ability to
- a. cause cancer.
- b. damage host cells.
- c. replicate in host cells.
- d. spread from one host cell to another.
9. An example of a virus that causes a persistent infection is
- a. Herpes Simplex I.
- b. HIV.
- c. Measles.
- d. Rotavirus.
10. Which of the following techniques would give you the most detailed views of a bacterial cell surface?
- a. Brightfield Illumination light microscopy.
- b. Darkfield Illumination light microscopy.
- c. Phase-Contrast microscopy.
- d. Scanning electron microscopy.
11. Valley fever is an endemic disease, which means that it
- a. is airborne.
- b. is continuously present in certain geographic areas.
- c. is caused by an endospore.
- d. infects large numbers of people annually.
12. The morphology of the virus shown above is
- a. complex.
- b. enveloped.
- c. helical.
- d. icosahedral.
13. The _____________ stain will give you information about the amount of peptidoglycan in the bacterial cell wall.
- a. capsule stain
- b. flagella stain
- c. gram stain
- d. spore stain
14. Bacteria that are pleomorphic
- a. are archaea.
- b. are motile.
- c. can assume many different shapes.
- d. do not have cell membranes.
15. Bacterial cells use their glycocalyx for
- a. avoiding attachment.
- b. keeping water out of the bacterial cell.
- c. phagocytosis.
- d. sticking to surfaces and other bacteria in biofilms.
16. Chloroplasts are necessary for
- a. electron storage.
- b. motility.
- c. photosynthesis.
- d. reproduction.
17. Rotaviruses cause a gastrointestinal disease that is transmitted through food and water and may cause dehydration due to severe diarrhea. If adequate fluids are taken, the infected person usually recovers in a few days. This is an example of a(n) ____________ infection.
- a. acute
- b. persistent
- c. recurrent
- d. serious
18. Protozoans are
- a. a symbiotic association of algae and fungi.
- b. photosynthetic.
- c. prokaryotes.
- d. unicellular.
19. The advantages of living in a biofilm include all of the following EXCEPT
- a. access to waste products from other microbes that can be used for food.
- b. decreased sensitivity to antibiotics (ability to live at higher antibiotic doses).
- c. life in a pure culture of a single microbe type.
- d. protection from engulfment by amoebas (in the environment) or white blood cells (in the body).
20. Fungi
- a. are mostly pathogenic (disease-causing).
- b. are photosynthetic.
- c. often produce neurotoxins.
- d. that are pathogenic often cause cutaneous (skin and nail) infections.
21. Adenovirus is a DNA virus. That means that adenovirus
- a. has a DNA genome.
- b. is composed entirely of DNA.
- c. must carry a DNA-dependent DNA polymerase in its capsid.
- d. uses DNA instead of RNA in its ribosomes.
22. The organism that ferments milk into yogurt is
- a. Escherichia coli.
- b. Lactobacillus acidophilus.
- c. Staphylococcus aureus.
- d. Plasmodium falciparium.
23. (WHITE) If this picture were in color, the bacteria would be purple. From that information and the micrograph, you can tell that
- a. the bacteria are bacilli.
- b. the bacteria have a thick peptidoglycan cell wall.
- c. the bacteria may be Lactobacillus acidophilus, which are Gram positive rods.
- d. All of the above are true.
23. (GREEN) If this picture were in color, the bacteria would be purple. From that information and the micrograph, you can tell that
- a. the bacteria are bacilli.
- b. the bacteria have a thick peptidoglycan cell wall.
- c. the bacteria may be Bacillus subtilis, which produce endospores.
- d. All of the above are true.
24. Helminths are
- a. single-celled protists.
- b. multi-cellular animals.
- c. obligate intracellular parasites.
- d. viruses.
25. The process shown above is for
- a. bacterial isolation.
- b. differential culture.
- c. motility test.
- d. None of the above.
26. Flagella
- a. allow bacteria to move towards food and away from toxins.
- b. are found on both eukaryotic and prokaryotic cells.
- c. can be used to identify subgroups (serovars) of bacteria.
- d. All of the above are true.
27. The uninoculated tube on the right is purple (neutral pH), while the inoculated one on the left is yellow (acidic) and some CO2 gas has collected from bacterial metabolism of the sugar. This is an example of a(n) __________ medium.
- a. basic
- b. differential
- c. enriched
- d. selective
Question: I am confused why the answer is B, because a differential medium distinguishes
between two microbes growing on the same media, but there is no evidence of
differential growth. It seems it could just be one microbe causing the acidity
and producing CO2 gas. I figured the answer was A, basic, because it is simply
allowing the microbe to grow.
What is it about the sample that would tell us it is differential???
Answer: When you do a differential test you don't always need to test all microbes - you just need to know what the results would be for the microbes you are trying to differentiate. For example, if the sugar is lactose and I have a Gram negative rod, I know that E. coli will ferment lactose and Salmonella or Shigella will not. If my unknown bacterium ferments lactose, it is more likely to be E. coli than Salmonella or Shigella. I would probably need several different tests to be sure of the identity of my unknown.
If I just wanted growth, I would not include a pH indicator; I would just look for turbidity (in a tube) or colonies (on a plate).
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28. To correctly identify the microbe that is causing an infection, the MOST important step is to ___________ it.
- a. culture
- b. dilute
- c. isolate
- d. observe
29. Gram negative but not Gram positive bacteria have
- a. an outer membrane containing lipopolysaccharide (LPS).
- b. a thick peptidoglycan cell wall.
- c. capsules.
- d. endospores.
30. Retroviruses
- a. cause recurrent infections.
- b. evolved before DNA viruses.
- c. use DNA-dependent RNA polymerases to produce DNA.
- d. use RNA-dependent DNA polymerases to produce DNA.
Part 2 ESSAY: Answer 2 of the questions below in the space provided. Each correct answer is worth five points, for a Part 2 total of 10 points.
31. Dr. Collins’ hand became red and swollen from an infected cut. List three properties of the infecting organism that could be used to identify it as the bacterium Nocardia braziliensis.
-
any 3 categories = full credit; 2 = 4 points; 1 = 2 points
- Morphology: size, shape, gram stain, colony shape and color
- Growth conditions: medium, oxygen, temperature
- Biochemistry: breakdown of certain sugars, amino acids
- DNA sequence, genetics
- Antigens, immunological proterties
32. Describe Coccidioides immitis and the disease it causes.
- 1 point apiece for up to 5 points total; must ID as fungus for 5 points
- fungus
- lives in soil
- makes spores
- transmitted in dust/wind
- not contagious
- causes Valley Fever
- usually respiratory disease
- flu-like symptoms
- can spread to other organs
- endemic in SW US, especially Arizona and California
33. What are the two most important properties of viruses and why?
- Viruses rapidly replicate within host cells to produce more viruses
- Viruses spread from one host to another via coughing, diarrhea, etc.
- Viruses are obligate intracellular parasites, not “alive” outside of host cells
- Viruses have DNA OR RNA, not both
- Viruses are usually species- and tissue-specific due to binding of spikes to host cell molecules
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