Microbiology The Human Experience by Foster-Test Bank

 

 

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Sample Test

Chapter 03: Observing Microbes

 

MULTIPLE CHOICE

 

1.    Resolution is

2.    the ability to detect individual cells.

3.    using a microscope to be seen.

4.    increasing the size of an image.

5.    the smallest distance two objects can be separated and still be distinguished.

 

 

ANS:      D             DIF:        Easy       REF:       3.1

OBJ:       3.1a Explain how magnification improves resolution of a microscopic image.

MSC:     Remembering

 

2.    Which of the following equals one millimeter?

3.    10-3 m c. 10-9 m

4.    10-6 m d. 10-12 m

 

 

ANS:      A             DIF:        Easy       REF:       3.1

OBJ:       3.1a Explain how magnification improves resolution of a microscopic image.

MSC:     Remembering

 

3.    Which of the following statements is INCORRECT?

4.    In fluorescence microscopy, fluorescent-labeled cellular structures are identified.

5.    In light microscopy, the object appears light against a dark background.

6.    In phase-contrast microscopy, organelles appear as light/dark patterns by variation in refractive indexes.

7.    Electron microscopy uses electrons to visualize the specimen.

 

 

ANS:      B             DIF:        Moderate           REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Analyzing

 

4.    In a compound microscope, which is the accurate pathway of light?

5.    light source, condenser, objective, specimen, eyepiece

6.    condenser, light source, eyepiece, specimen, objective

7.    eyepiece, objective, specimen, condenser, light source

8.    light source, condenser, specimen, objective, eyepiece

 

 

ANS:      D             DIF:        Easy       REF:       3.3

OBJ:       3.3a Explain the use of a bright-field microscope.              MSC:     Remembering

 

5.    Which microscope is used to observe specific fluorescent-labeled structures?

6.    a compound light microscope c.             a fluorescence microscope

7.    a phase-contrast microscope d.            an electron microscope

 

 

ANS:      C             DIF:        Easy       REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Remembering

 

6.    What is the total magnification of a specimen viewed with a 10x ocular lens and a 35x objective lens?

7.    10x c.             350x

8.    3.5x d.            3,500x

 

 

ANS:      C             DIF:        Moderate           REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Applying

 

7.    In the figure below, line “B” points to the microscope’s

 

1.    ocular lens. c.             condenser.

2.    objective. d.            light source.

 

 

ANS:      B             DIF:        Easy       REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Remembering

 

8.    In the figure below, line “C” points to the microscope’s

 

1.    ocular lens. c.             condenser.

2.    objective. d.            light source.

 

 

ANS:      C             DIF:        Easy       REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Remembering

 

9.    In the figure below, line “D” points to the microscope’s

 

1.    ocular lens. c.             condenser.

2.    objective. d.            light source.

 

 

ANS:      D             DIF:        Easy       REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Remembering

 

10.  You are performing a Gram stain to differentiate between Gram-positive and Gram-negative bacteria. At the end of the procedure, a Gram-positive cell will appear

11.  purple. c. pink.

12.  colorless. d.            blue.

 

 

ANS:      A             DIF:        Easy       REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Understanding

 

11.  You complete a Gram stain on Gram-positive bacteria; however, you over-decolorize your sample. What color will your bacteria be at this point?

12.  purple c.             pink

13.  colorless d.            blue

 

 

ANS:      C             DIF:        Difficult                REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Analyzing

 

12.  Which of the following is the correct order of the Gram-stain regents?

13.  iodine, crystal violet, safranin, ethanol

14.  ethanol, crystal violet, safranin, iodine

15.  crystal violet, ethanol, iodine, safranin

16.  crystal violet, iodine, ethanol, safranin

 

 

ANS:      D             DIF:        Moderate           REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Applying

 

13.  In Gram-negative cells, which layer is disrupted by the decolorizer in the Gram-staining procedure?

14.  techoic acids c.             peptidoglycan

15.  outer membrane d.            mycolic acid

 

 

ANS:      B             DIF:        Moderate           REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Understanding

 

14.  You are performing a Gram stain on Gram-positive bacteria and you stop after the addition of the mordant. What is the appearance of the bacteria at this point?

15.  purple c.             pink

16.  colorless d.            blue

 

 

ANS:      A             DIF:        Moderate           REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Understanding

 

15.  You are performing a Gram stain on Gram-positive bacteria and you stop after the addition of the counterstain. What is the appearance of the bacteria at this point?

16.  purple c.             pink

17.  colorless d.            blue

 

 

ANS:      A             DIF:        Moderate           REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Understanding

 

16.  What is the purpose of fixation in a staining procedure?

17.  to preserve the organisms c.             to impart color to the sample

18.  to adhere bacterial cells to the slide d.            to heat the sample

 

 

ANS:      B             DIF:        Easy       REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Remembering

 

17.  The cell wall of Gram-positive bacteria contain(s)

18.  only a single layer of peptidoglycan.

19.  a thick layer of lipopolysaccharides.

20.  a thinner and more porous cell wall than Gram-negative species.

21.  a thick layer of peptidoglycan.

 

 

ANS:      D             DIF:        Easy       REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Remembering

 

18.  Which of the following is FALSE about a properly completed Gram stain?

19.  It is a key tool used in the identification of bacterial species.

20.  It is reliable only for fresh cultures.

21.  It differentiates bacteria based on their cell wall components.

22.  At the completion of the stain, Gram-negative cells stain purple.

 

 

ANS:      D             DIF:        Easy       REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Understanding

 

19.  Assume you stain Bacillus with malachite green with heat and then counterstain with safranin. What type of stain would you be performing?

20.  a differential and endospore stain c.             a simple and endospore stain

21.  a differential and Gram stain d.            a simple and Gram stain

 

 

ANS:      A             DIF:        Easy       REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Remembering

 

20.  Assume you stain Bacillus with malachite green with heat and then counterstain with safranin. Through the microscope, the green structures are

21.  cell walls. c.             endospores.

22.  capsules. d.            bacteria.

 

 

ANS:      C             DIF:        Easy       REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Understanding

 

21.  You are observing a bacterial specimen on the 100x objective but have forgotten to put the immersion oil on the slide. The specimen will appear

22.  smaller with better resolution.

23.  larger with poor resolution.

24.  somewhat fuzzy with poor resolution.

25.  the same.

 

 

ANS:      C             DIF:        Moderate           REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Understanding

 

22.  The purpose of the condenser is to

23.  focus light rays onto the slide.

24.  magnify the image from the objective lens.

25.  decrease the refractive index.

26.  improve resolution.

 

 

ANS:      A             DIF:        Easy       REF:       3.3

OBJ:       3.3a Explain the use of a bright-field microscope.              MSC:     Remembering

 

23.  Which of the following is INCORRECT?

24.  Congo red is a negative stain.

25.  Malachite green is an acid-fast stain.

26.  Methylene blue is a simple stain.

27.  Fluorophore is in an antibody stain.

 

 

ANS:      B             DIF:        Difficult                REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Analyzing

 

24.  Which of the following depicts the steps of the Gram stain in the correct order?

25.  crystal violet, ethanol, iodine, safranin

26.  safranin, iodine, ethanol, crystal violet

27.  crystal violet, iodine, ethanol, safranin

28.  safranin, ethanol, iodine, crystal violet

 

 

ANS:      C             DIF:        Moderate           REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Understanding

 

25.  A(n) ________ microscopy microscope produces halos of bright lights against a dark field.

26.  compound light c.             fluorescence

27.  electron d.            darkfield

 

 

ANS:      D             DIF:        Easy       REF:       3.5

OBJ:       3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.                        MSC:     Remembering

 

26.  Which of the following is powerful enough to visualize ribosomes?

27.  a compound light microscope c.             a fluorescence microscope

28.  an electron microscope d. a darkfield microscope

 

 

ANS:      B             DIF:        Easy       REF:       3.5

OBJ:       3.5b Describe how electron microscopy enables visualization of objects below the resolution limit of light, such as viruses and parts of cells.                             MSC:     Remembering

 

27.  Which of the following is FALSE concerning darkfield microscopy?

28.  Contamination in the medium can scatter light.

29.  It can be used to identify spirochetes.

30.  Images are dark against a light background.

31.  High resolution cannot be achieved.

 

 

ANS:      C             DIF:        Moderate           REF:       3.5

OBJ:       3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.                        MSC:     Understanding

 

28.  What is an advantage of fluorescence microscopy?

29.  It allows for the preservation of the specimen.

30.  It provides the greatest resolution.

31.  It has the ability to stain live specimens.

32.  It has the ability to detect specific microbes.

 

 

ANS:      D             DIF:        Easy       REF:       3.5

OBJ:       3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.                        MSC:     Remembering

 

29.  Which image shows Giardia lamblia visualized with a scanning electron microscope?

 

1.    1 c.             3

2.    2 d.            4

 

 

ANS:      C             DIF:        Moderate           REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Understanding

 

30.  Which images display organelles?

 

1.    1 and 2 c.             1 and 3

2.    2 and 4 d.            3 and 4

 

 

ANS:      B             DIF:        Moderate           REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Applying

 

31.  Which microscope best allows the observation of internal cell structures in a natural state?

32.  compound light microscope c.             darkfield microscope

33.  phase-contrast microscope d.            electron microscope

 

 

ANS:      B             DIF:        Moderate           REF:       3.5

OBJ:       3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.                        MSC:     Understanding

 

32.  Which of the following statements is correct?

33.  Safranin is a primary stain. c.             Ethanol is a decolorizer.

34.  Iodine is a counterstain. d.            Crystal violet is a mordant.

 

 

ANS:      C             DIF:        Moderate           REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Understanding

 

33.  If a microbiologist forgot to heat-fix a bacterial smear before staining, what would probably happen?

34.  Bacteria might wash off the slide.

35.  The stain would not stick to the bacteria.

36.  The bacteria might decolorize too quickly.

37.  The color of the stain would be too dark to see the bacteria.

 

 

ANS:      A             DIF:        Moderate           REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Understanding

 

34.  Why is the presence of a capsule clinically significant?

35.  It protects the bacterial cell from lack of nutrients.

36.  It protects the bacterial cell from engulfment by white blood cells.

37.  It protects the bacterial cell from heat.

38.  It protects the bacterial cell from the staining regents.

 

 

ANS:      B             DIF:        Moderate           REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Understanding

 

35.  In the figure below, which depicts cocci in chains?

 

1.    1 c.             3

2.    2 d.            none of the labeled areas

 

 

ANS:      C             DIF:        Easy       REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Understanding

 

36.  Which type of stain would be the most useful in helping clinicians decide which class of antibiotics to prescribe?

37.  negative stain c.             endospore stain

38.  simple stain d.            Gram stain

 

 

ANS:      D             DIF:        Difficult                REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Analyzing

 

37.  Which of the following is mismatched?

38.  darkfield microscopy—uses visible light

39.  fluorescence microscopy—uses a fluorescent light

40.  scanning electron microscopy—produces a three-dimensional image

41.  compound light microscopy—produces a light image against a dark background

 

 

ANS:      B             DIF:        Difficult                REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Analyzing

 

38.  Which microscope uses variations in refractive indexes to display specimens?

39.  bright-field c.             phase-contrast

40.  fluorescence d.            transmission electron

 

 

ANS:      C             DIF:        Easy       REF:       3.5

OBJ:       3.5b Describe how electron microscopy enables visualization of objects below the resolution limit of light, such as viruses and parts of cells.                             MSC:     Applying

 

39.  In the Gram stain, which step is critical in differentiating Gram-positive from Gram-negative cells?

40.  crystal violet c.             mordant

41.  safranin d.            ethanol

 

 

ANS:      D             DIF:        Moderate           REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Analyzing

 

40.  Which microscope technique is best used for visualizing the surface structures of cells and viruses?

41.  phase-contrast c. scanning electron

42.  bright-field d.            darkfield

 

 

ANS:      C             DIF:        Moderate           REF:       3.5

OBJ:       3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.                        MSC:     Understanding

 

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

42.  Crystal violet differentially stains Gram-positive cells.

43.  Gram’s iodine differentially stains Gram-positive cells.

44.  Ethanol differentially destains Gram-negative cells.

45.  Safranin differentially stains Gram-negative cells.

 

 

ANS:      C             DIF:        Difficult                REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Analyzing

 

42.  Oil immersion is used in which type of microscopy and on which objective?

43.  bright-field microscopy, 40X c.             darkfield microscopy, 40x

44.  bright-field microscopy, 100x d.            darkfield microscopy, 100x

 

 

ANS:      B             DIF:        Easy       REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Remembering

 

43.  Using the figure below, which of the following images depicts the refraction of light?

 

1.    1 c.             3

2.    2 d.            4

 

 

ANS:      C             DIF:        Moderate           REF:       3.2

OBJ:       3.2a Explain how light interacts with an object.   MSC:     Applying

 

44.  Using the figure below, which of the following images depicts the absorption of light?

 

1.    1 c.             3

2.    2 d.            4

 

 

ANS:      A             DIF:        Moderate           REF:       3.2

OBJ:       3.2a Explain how light interacts with an object.   MSC:     Applying

 

45.  The bending of light as it enters a substance that slows its speed is known as

46.  reflection. c.             absorption.

47.  refraction. d.            scattering.

 

 

ANS:      B             DIF:        Moderate           REF:       3.2

OBJ:       3.2b Describe how refraction enables magnification, and explain the limits to magnification and resolution.                MSC:     Remembering

 

46.  CASE HISTORY

Jared, a 48-year-old, previously healthy man, was admitted to a hospital in Columbus, Ohio, after six days of increasing dyspnea (shortness of breath) and watery diarrhea. Jared also complained of a dry cough, myalgia (muscle pain), nausea, and vomiting. He appeared flushed and had dry mucous membranes. His temperature was 39°C (102.2°F), and his pulse rate was 103 beats per minute. Chest radiographs showed pneumonia with consolidation (formation of a firm mass) of the left lower lobe. His c-reactive protein (crP, a blood protein produced by the liver) was greater than 220 milligrams per liter (mg/l), a high level that indicates inflammation.

Before onset of symptoms, Jared recalled having cleaned the filter of an outdoor whirlpool spa. Culture from Jared’s sputum and from the spa filter revealed Gram-negative bacilli consistent with Legionella pneumophila. The diagnosis was confirmed by fluorescence microscopy using direct fluorescent antibody (DFA) stain. The patient received intravenous amoxicillin and clarithromycin antibiotics for eight days before his condition returned to normal.

 

If the technician conducting the Gram stain in this case study had left ethanol on the prepared slide longer than necessary, what might be the effect on this slide and identification?

 

1.    The bacteria on the slide may have been decolorized Gram-positive bacilli.

2.    None. The timing of ethanol does not affect the outcome of a Gram stain.

3.    None, since the bacteria appear Gram negative, they could not have been over-decolorized.

4.    The bacteria on the slide may have been cocci rather than bacilli.

 

 

ANS:      C             DIF:        Moderate           REF:       Case History 3.2

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Analyzing

 

COMPLETION

 

1.    A ________ is the only way to observe live specimens.

 

ANS:      wet mount

 

DIF:        Moderate           REF:       3.3          OBJ:       3.3a Explain the use of a bright-field microscope.

MSC:     Remembering

 

2.    In an acid-fast stain, carbolfuchsin specifically stains ________ of Mycobaterium tuberculosis.

 

ANS:      mycolic acid

 

DIF:        Easy       REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Remembering

 

3.    Bacteria that grow as rods are commonly referred to as ________, whereas bacteria that grow as spheres are known as ________.

 

ANS:      bacilli; cocci

 

DIF:        Easy       REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Remembering

 

4.    Refraction occurs by the ________ of light and is the key property enabling a lens to magnify an image.

 

ANS:      bending

 

DIF:        Easy       REF:       3.2          OBJ:       3.2a Explain how light interacts with an object.

MSC:     Remembering

 

5.    Using a compound microscope, the image is magnified at the ________ and the ________.

 

ANS:

objective lens; ocular lens

ocular lens, objective lens

 

DIF:        Easy       REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Understanding

 

6.    Electron microscopy uses beams of ________ to generate high-resolution images.

 

ANS:      electrons

 

DIF:        Easy       REF:       3.5

OBJ:       3.5b Describe how electron microscopy enables visualization of objects below the resolution limit of light, such as viruses and parts of cells.                             MSC:     Remembering

 

7.    Immersion oil is used with the ________ objective.

 

ANS:      100x

 

DIF:        Easy       REF:       3.3

OBJ:       3.3b Describe how to observe an object in focus by using a compound microscope.

MSC:     Remembering

 

8.    1mm = ________ m

 

ANS:

0.001

10 -3

 

DIF:        Easy       REF:       3.1

OBJ:       3.1a Explain how magnification improves resolution of a microscopic image.

MSC:     Remembering

 

9.    Magnification without increase in resolution is called ________.

 

ANS:      empty magnification

 

DIF:        Easy       REF:       3.2

OBJ:       3.2b Describe how refraction enables magnification, and explain the limits to magnification and resolution.                MSC:     Remembering

 

SHORT ANSWER

 

1.    What is the difference between a simple and a differential stain? Give one example of a simple stain and one example of a differential stain.

 

ANS:

A simple stain uses one dye and does not impart color to other tissue or the background. A differential stain, on the other hand, differentiates between objects by staining only particular types of cells or specific subcellular structures and often stains two cells differently.

An example of a simple stain is methylene blue or crystal violet.

An example of a differential stain is the Gram stain or acid-fast stain.

 

DIF:        Moderate           REF:       3.4

OBJ:       3.4a Explain how a stain reveals additional information about a microscopic object.

MSC:     Understanding

 

2.    What is the purpose of the mordant in the Gram-stain procedure?

 

ANS:

The iodine solution used in the Gram stain contains iodine ions. These ions bind to the crystal violet trapped inside the bacterial cells. This is held more tightly within the cell wall and resists decolorization by the alcohol solution.

 

DIF:        Moderate           REF:       3.4

OBJ:       3.4b Describe how the Gram stain distinguishes two classes of bacteria.

MSC:     Applying

 

3.    The size at which objects become visible depends on the resolution of the observer’s eye. Typically eagles can resolve objects much smaller or farther away than humans can. Please explain why.

 

ANS:

Resolution is achieved by focusing an image on the photoreceptors in the retina of the eye. The retina of eagles has more tightly packed photoreceptors compared to humans. So an eagle’s eye can resolve objects smaller or farther away than the human eye can.

 

DIF:        Difficult                REF:       3.1

OBJ:       3.1b Explain what can be learned from different kinds of microscopy.

MSC:     Applying

 

4.    Compare and contrast darkfield, phase-contrast, and fluorescence microscopy.

 

ANS:

Darkfield, phase-contrast, and fluorescence microscopy are all types of light microscopy. Darkfield uses a special condenser that blocks out transmitted light from the specimen; therefore, the image appears light against a black background. Phase-contrast also uses light; however, because of the high concentration of solutes, the light is refracted differently throughout the cell. Fluorescence microscopy allows the visualization of specific cellular molecules within the sample. Visible light is used along with fluorescent dyes, which stain the specimen. These fluorophores are excited with different wavelengths of light and emit colors.

 

DIF:        Difficult                REF:       3.5

OBJ:       3.5a Describe the different kinds of information obtained by dark-field, phase-contrast, and fluorescence microscopy.                        MSC:     Analyzing

 

5.    Please label the figure below with different interactions of light with matter. Please describe what is happening with each interaction.

 

 

ANS:

1.    Absorption: Label light wave and heat increasing. Description: Absorption occurs when the energy is acquired or absorbed by the object. Energy is converted to heat.

 

2.    Reflection: Label light waves with incident angle and angle of reflection. Description: Reflection occurs when the wave bounces off the surface at an angle equal to its incident angle.