General Microbiology Multiple Choice Questions

MCQ-General Microbiology

1. Cell wall synthesis during cell growth involves insertion of what material into the existing wall material.

a. DAP. b. Peptidoglycan.

c. bactoprenol. d. lipopolysaccharide.

2. Heat stable proteins tend to have………. which probably leads to more……..

a. Hydrophilic cores / ionic dispersal of particles which would normally cluster.

b. Hydrophobic cores / "salt bridges" between hydrophilic amino acids on the surface.

c. Hydrophobic cores / ionic dispersal of particles which would normally cluster.

d. Hydrophilic cores / "salt bridges" between hydrophilic amino acids on the surface.

3. The significance of Hopanoids in the plasma membrane is that

a. It selectively allows some molecules to pass into the organism

b. It prevents movement of molecules out of the organism

c. It provides the elasticity to the membrane d. All of the above

4. Arrange the following terms in the order they would be found if you traveled from the cytoplasm to the external medium of a Gram negative cell possessing a capsule:

1. periplasmic space 2. phospholipid bilayer of the outer membrane

3. O-polysaccharide 4. cytoplasmic membrane

5. capsule

a. 4,3,1,2,5 b. 4,1,2,3,5

c. 5,2,3,1,4 d. 5,3,2,1,4

5. Osmotolerant yeasts are able to grow at high salt concentrations because their cytoplasm contains high concentrations of

a. High sodium ions

b. Amino acids.

c. Lipids. d. polyalcohols like glycerol

6. Magnetosomes, glycogen, polyphosphate and poly-beta-hydoxybutyric acid are all types of:

a. Storage products.

b. Cytoplasmic inclusions.

c. Cell wall inclusions

d. Both b and c

7. Presence of sodium taulocholate in Mc Conkey agar makes the media

a. Differential media

b. Basal media

c. Selective media

d. Enriched media

8. What is the main function of central mesosome in Gram positive bacteria?

a. Site of protein synthesis.

b. Transport of extracelluar enzymes outside the cell wall

c. Taking part in cell division and DNA replication

d. Protect the cell membrane from injuries

9. The third amino acid in the peptidoglycan crosslinking chain is either diaminopamilic acid or lysine because this amino acid must

a. Be positively charged for a salt bridge to form.

b. Be hydrophillic.

c. Have a free amino group for peptide bond formation.

d. Have a large R-side chain to fill space in the cell wall.

10. The outer membrane of Gram negative cells is more permeable than the plasma membrane because

a. LPS is larger than most membrane phospholipids.

b. Lipoproteins stretch the outer membrane.

c. Porin proteins establish holes in the outer membrane.

d. The core polysaccharide spans the lipid bilayer.

11. The bacterial capsule

a. may be antigenic

b. is required for cell viability

c. is involved in motility.

d. may contribute to a bacterium's pathogenicity

12. Bacterial pili may enhance virulence of bacterial pathogens by

a. Transporting nutrients

b. providing a means of attachment

c. increasing the surface area of bacteria.

d. being an endotoxin

13. An aquatic bacterium with a polysaccharide capsule for attachment and virulence is

a. Stella spp. b. Caulobacter spp.

c. Streptococcus mutans d. Sphaerotilus natans

14. Which of the following statements about bacterial flagella is incorrect?

a. The locomotion caused by flagella can be directed to move cells toward a source of nutrients.

b. The filaments are composed of protein subunits called flagellin.

c. The flagella move cells by acting as propellers.

d. All motile bacteria have flagella

e. Flagella increase in length by adding new material to the tip not the base

15. Transformation includes all of the following except

a. Plasmids.

b. Sex pili.

c. Competent cell.

d. Naked DNA.

16. Hfr bacteria

a. Are derived from F⁺ bacteria.

b. Functions as donor in crosses with F^- bacteria 40°C.

c. Functions as donor in crosses with F^- bacteria 40°C and are so called because they result in high frequency recombination

d. are so called because they result in high frequency recombination

17. Preserve foods by using salts and sugars works by

a. Depleting nutrients. b. Lowering osmotic pressure.

c. Creating a hypertonic environment. d. Creating a hypotonic environment.

18. Which one of the following forms of immunity to viruses would be least likely to be life long?

a. Passive immunity b. Passive-active immunity

c. Active immunity d. Cell mediated immunity

19. Which one of the following is not true for virus, obligate intracellular parasites?

a. Viruses cannot generate energy outside of cells

b. Viruses cannot synthesize proteins outside of cells

c. Viruses must degrade host cell DNA in order to obtain nucleotides

d. Enveloped viruses require host cell membrane to obtain their envelopes

20. Each of the following statement of lysogeny is correct except

a. Viral genes replicate independently of bacterial genes

b. Viral genes responsible for lysis are repressed

c. Viral DNA is integrated into bacterial DNA

d. Some lysogenic phages encode toxins that cause human disease

21. The genome of rhabdoviruses consists of a single-stranded RNA molecule whose sequence is complementary to the RNA sequence which functions as a messenger RNA. How is the "+ sense" messenger RNA produced in cells infected by rhabdovirus?

a. one portion of the infecting RNA is directly translated by host cell ribosomes

b. host cell RNA polymerase activity

c. reverse transcriptase activity

d. the infecting virus particle contains an RNA-dependent RNA polymerase

22. An E. coli cell which carries a lambda prophage is immune to a lytic infection by a second lambda virus because:

a. The second virus cannot inject its DNA

b. proteins from the prophage's lytic genetic program prevent replication of the second virus

c. proteins from the prophage's lysogenic genetic program prevent replication of the second virus

d. the second virus cannot adsorb to the cell

23. Which of the following methods will not sterilize?

a. 500 mg/L ethylene oxide at 50⁰C for 4 hours

b. Dry heat at 171⁰C for 1 to 2 hours

c. 121⁰C at 15 lb/in pressure for 15 to 20 minutes

d. 100⁰C boiling water for 30 minutes

24. Which of the following is bactericidal?

a. Ionizing radiation b. Freeze-drying c. Deep freezing

d. All of these processes kill bacteria.

25. Which of the following is most effective for sterilizing mattresses and plastic Petri plates?

a. Ethylene oxide b. Glutaraldehyde

c. Autoclave d. Ultraviolet radiation

Use this information to answer the following question(s): Q. 26
	Phenol Coefficient
Compound	Salmonella typhi	Staphylococcus aureus
Phenol	1	1
Cetylpyridinium chloride	228	337
Hexachlorophene	5-15	15-40
Merthiolate	600	62.5
Ethanol	0.04	0.04

26. Which disinfectant was the most effective against Salmonella?

a. Phenol b. Cetylpyridinium chloride

c. Hexachlorophene d. Merthiolate

27. If a 1:600 dilution of a test compound kills a standard population of Staphylococcus aureus in 10 minutes but not 5 minutes while a 1:60 dilution of phenol kills the population in the same time, what is the phenol coefficient of the test compound?

a. 1 b. 5 c. 10 d. 50

28. If a canning procedure is not properly followed, which type of microbe is most likely to grow in the canned food?

a. Acidophile b. Microaerophile

c. Mesophile d. Obligate Anaerobe

29. The time required to kill 90% of the microorganisms in a sample at a specific temperature is the

a. Decimal reduction time. b. Thermal death temperature.

c. F value. d. D value.

30. UV radiation might be an effective way to disinfect which of the following

a. Contaminated hamburger. b. distilled water in quartz tube

c. paper rapped glass wares d. a sealed box of soil.

31. If 90% of the population of bacteria that had 10⁶ CFU/ml are killed there will be ____ remaining CFU/ml.

a. 10⁷ b. 9 x 10⁵c. 10⁵d. 10

Compare the following entities (I and II).

32. I. The percentage of cells killed by a procedure with a D₁₀₀ value of 8 minutes

II. The percentage of cells killed by a procedure with a D₁₀₀ value of 5 minutes

a. I is greater than II b. I is less than II

c I is exactly or approximately equal to II.

d. I may stand in more than one of the above relations to II

33. Thirty-six colonies grew in nutrient agar from 1.0 ml of sample withdrawn from solution diluted to 10^-5 in a standard plate count procedure. How many cells per ml were in the original sample?

a. 3,600 b. 360,000 c. 1,800,000 d. 3,600,000

34. A bacterial population increases from 10³ to 10⁹in 10 hours. What is the generation time of this culture?

a. 30 minutes b. 45 minutes c. 60 minutes

d. Not enough information to determine the generation time

35. The steady-state level of biomass in a continuous culture is determined by:

a. the volume of the culture vessel.

e. the concentration of limiting substrate in the culture vessel.

c. the concentration of limiting substrate in the medium reservoir.

d. the dilution rate

36. Which is the most SENSITIVE method of enumerating microbes?

a. turbidity measurement b. Direct microscopic count

c. viable plate count d. dry weight basis

37. A microbiology student noticed that a Fluid Thioglycollate culture broth tube was very turbid at the surface and turbid throughout the rest of the tube. She can conclude that the

a. Broth is sterile. b. Organisms are aerobes.

c. Organisms should be put in a candle jar. d. Organisms are facultative anaerobes.

38. Arrange the following techniques in order of increasing stringency for maintaining anaerobic microbes.

1. addition of a reducing agent

2. use of an anaerobic jar

3. use of an anaerobic glove box

4. fill bottles completely with media

a. 1,2,3,4. b. 2,3,4,1.

c. 4,1,2,3 d. 3,2,1,4.

39. The substage condenser

a. Changes the wavelength of the light reaching the specimen

b. Focuses light on the specimen

c. Decreases the amount of light reaching the specimen

d. Increase and intensify the amount of light reaching the specimen.

40. Living, unstained cells and organisms can be observed best using

a. Fluorescent microscopy b. TEM

c. Phase contrast microscopy d. All of the above

41. Hanging drop method is used to observe…………………….of microorganisms.

a. motility b. germination c. fusion d. all of the above

42. Monochromatic (one color) light is sometimes used to increase the resolution of light microscopes. Light of which color below would give you the best resolution?

a. Red b. Orange c. Green d. Blue

43. Which of the following objectives would give you the best resolution of small objects?

a. 10x air, N.A. 0.25 b. 40x air, N.A. 0.65

c. 64x oil, N.A. 1.4 d. 100x oil, N.A. 1.25

44. Which of the following statements is most correct about the differential Gram stain?

a. Crystal violet differentially stains Gram positive cells.

b. Gram's iodine differentially stains Gram positive cells.

c. Acetone differentially destains Gram negative cells.

d. Saffron red differentially stains Gram negative cells.

45. Phase Contrast microscopy

a. Continuously changes the phase of the incident light from the condenser to improve contrast in the specimen.

b. Uses circular filters in the condenser and objective to give contrast to parts of the cell with different refractive indices.