Opening the book…
1. Both spirilla and spirochetes appear spiral-shaped. Which structural feature distinguishes them?
- a) Spirilla have rigid cell walls; spirochetes have flexible cell walls
- b) Spirilla have flexible cell walls; spirochetes have rigid cell walls
- c) Spirilla are larger than spirochetes
- d) Spirilla are Gram-positive; spirochetes are Gram-negative
Answer a) Spirilla have rigid cell walls; spirochetes have flexible cell walls
Spirilla have rigid cell walls, while spirochetes have flexible cell walls.
Spirilla have rigid cell walls, while spirochetes have flexible cell walls.
2. In addition to cell wall rigidity, spirilla can be differentiated from spirochetes by the presence of:
- a) Endospores
- b) External flagella
- c) A capsule
- d) Mycolic acids
Answer b) External flagella
Spirilla can also be differentiated from spirochetes due to the presence of external flagella.
Spirilla can also be differentiated from spirochetes due to the presence of external flagella.
3. Spirochetes possess structures that allow their cells to rotate in a corkscrew manner. These structures are called:
- a) External flagella
- b) Axial filaments (endoflagella)
- c) Endospores
- d) Capsules
Answer b) Axial filaments (endoflagella)
Spirochetes have structures known as axial filaments (endoflagella) that allow their cells to rotate in a corkscrew manner.
Spirochetes have structures known as axial filaments (endoflagella) that allow their cells to rotate in a corkscrew manner.
4. A bacterium that appears as a short, plump rod with a shape intermediate to that of a coccus and a bacillus is called a:
- a) Vibrio
- b) Coccobacillus
- c) Spirillum
- d) Palisade
Answer b) Coccobacillus
Coccobacillus bacteria have a shape intermediate to that of a coccus and a bacillus; they appear as short plump rods.
Coccobacillus bacteria have a shape intermediate to that of a coccus and a bacillus; they appear as short plump rods.
5. Bacterial cellular arrangement is dependent on which of the following? Select all that apply.
- a) The plane of cell division
- b) Whether cells remain attached to one another following cell division
- c) The type of stain used to visualize the cells
- d) The magnification at which the cells are viewed
Answers: a) The plane of cell division; b) Whether cells remain attached to one another following cell division
Cellular arrangement depends on the plane of cell division and whether cells remain attached to one another following cell division.
Cellular arrangement depends on the plane of cell division and whether cells remain attached to one another following cell division.
6. Why are more arrangements observed among cocci than among bacilli?
- a) Cocci reproduce more rapidly than bacilli
- b) Cocci may divide in a single plane, in two perpendicular planes, or in many planes, while bacilli divide only in the transverse plane
- c) Cocci are smaller and can pack together more tightly
- d) Bacilli never remain attached after division
Answer b) Cocci may divide in a single plane, in two perpendicular planes, or in many planes, while bacilli divide only in the transverse plane
Some cocci divide in a single plane, others in two perpendicular planes, and still others in many planes, producing a variety of arrangements. Bacilli divide only in the transverse plane.
Some cocci divide in a single plane, others in two perpendicular planes, and still others in many planes, producing a variety of arrangements. Bacilli divide only in the transverse plane.
7. Spirilla are generally observed as individual cells because they:
- a) Rarely remain attached to one another after division
- b) Divide in many planes
- c) Are always motile
- d) Cannot be stained
Answer a) Rarely remain attached to one another after division
Spirilla rarely remain attached, so they are generally observed as individual cells.
Spirilla rarely remain attached, so they are generally observed as individual cells.
8. Fixation is performed on a smear for which of the following purposes? Select all that apply.
- a) To attach the cells to the slide so they are not rinsed off during staining
- b) To prevent distortion of the cells that would alter their morphology
- c) To kill the cells, making the sample safer to handle
- d) To increase the total magnification of the specimen
Answers: a) To attach the cells to the slide so they are not rinsed off during staining; b) To prevent distortion of the cells that would alter their morphology; c) To kill the cells, making the sample safer to handle
Fixation attaches the cells to the slide, prevents distortion that would alter morphology, and kills the cells, making the sample safer to handle.
Fixation attaches the cells to the slide, prevents distortion that would alter morphology, and kills the cells, making the sample safer to handle.
9. Chemical fixation is accomplished by applying which type of reagent to the sample?
- a) Methyl alcohol or formaldehyde
- b) Crystal violet or safranin
- c) Acid-alcohol
- d) Isotonic saline
Answer a) Methyl alcohol or formaldehyde
Chemical fixation is accomplished by applying a chemical reagent such as methyl alcohol or formaldehyde.
Chemical fixation is accomplished by applying a chemical reagent such as methyl alcohol or formaldehyde.
10. Heat fixation is correctly performed by:
- a) Holding the wet smear directly in the flame until it steams
- b) Passing the air-dried smear back and forth over the flame of a Bunsen burner, smear side up
- c) Placing the slide on a steam bath for five minutes
- d) Submerging the slide in boiling water
Answer b) Passing the air-dried smear back and forth over the flame of a Bunsen burner, smear side up
Heat fixation is done by passing the air-dried smear back and forth over the flame of a Bunsen burner, smear side up.
Heat fixation is done by passing the air-dried smear back and forth over the flame of a Bunsen burner, smear side up.
11. What is the primary reason specimens are stained before microscopic observation?
- a) To increase the resolution of the objective lens
- b) To add contrast to the cells, allowing them to be viewed with the microscope
- c) To kill any pathogens present on the slide
- d) To make the cells adhere to the slide
Answer b) To add contrast to the cells, allowing them to be viewed with the microscope
Samples are stained in order to add contrast to the cells, allowing them to be viewed using the microscope.
Samples are stained in order to add contrast to the cells, allowing them to be viewed using the microscope.
12. Which of the following are examples of acidic (anionic) dyes? Select all that apply.
- a) India ink
- b) Nigrosine
- c) Eosin
- d) Methylene blue
- e) Crystal violet
Answers: a) India ink; b) Nigrosine; c) Eosin
India ink, nigrosine, and eosin are acidic (anionic) dyes. Methylene blue and crystal violet are basic (cationic) dyes.
India ink, nigrosine, and eosin are acidic (anionic) dyes. Methylene blue and crystal violet are basic (cationic) dyes.
13. Why does the interior of a bacterial cell carry an overall negative charge?
- a) The cell wall is composed of peptidoglycan
- b) Cells are filled with negatively charged molecules such as proteins and nucleic acids
- c) The cell membrane is made of lipids
- d) Water molecules inside the cell are polar
Answer b) Cells are filled with negatively charged molecules such as proteins and nucleic acids
Cells are filled with molecules such as proteins and nucleic acids that are negatively charged, giving the cell an overall negative charge internally.
Cells are filled with molecules such as proteins and nucleic acids that are negatively charged, giving the cell an overall negative charge internally.
14. When an anionic dye is applied to a bacterial smear, what is the expected result?
- a) The dye is repelled by the cell and stains the surrounding background
- b) The dye ionically bonds to structures inside the cell, staining the cell
- c) The dye stains only the cell wall
- d) The dye stains both the cell and the background equally
Answer a) The dye is repelled by the cell and stains the surrounding background
An anionic dye is repelled by the negatively charged cell, so it stains the background surrounding the cell.
An anionic dye is repelled by the negatively charged cell, so it stains the background surrounding the cell.
15. Differential staining procedures differ from simple staining procedures in that differential stains:
- a) Make use of two stains rather than just one
- b) Require the use of an oil immersion lens
- c) Do not require fixation of the smear
- d) Can determine the genus and species of a bacterium
Answer a) Make use of two stains rather than just one
Differential staining techniques make use of two stains rather than just one, and allow the observer to obtain additional information about the sample.
Differential staining techniques make use of two stains rather than just one, and allow the observer to obtain additional information about the sample.
16. The primary stain used in the Gram stain procedure is:
- a) Safranin, an acidic stain
- b) Crystal violet, a basic stain
- c) Carbolfuchsin, a lipid-soluble stain
- d) Malachite green, a basic stain
Answer b) Crystal violet, a basic stain
The primary stain in the Gram stain is crystal violet, a basic stain that stains both Gram-positive and Gram-negative cells.
The primary stain in the Gram stain is crystal violet, a basic stain that stains both Gram-positive and Gram-negative cells.
17. What is the function of the mordant, Gram's iodine, in the Gram stain procedure?
- a) It removes the primary stain from Gram-negative cells
- b) It binds to crystal violet, forming an insoluble complex that is trapped within the cell
- c) It stains cells that have lost the primary stain
- d) It dissolves the outer membrane of Gram-negative cells
Answer b) It binds to crystal violet, forming an insoluble complex that is trapped within the cell
Mordants help fix dyes into the sample. Gram's iodine binds to crystal violet, forming an insoluble complex trapped within the cell.
Mordants help fix dyes into the sample. Gram's iodine binds to crystal violet, forming an insoluble complex trapped within the cell.
18. Which reagent constitutes the differential step of the Gram stain procedure?
- a) Crystal violet
- b) Gram's iodine
- c) Gram's decolorizer
- d) Safranin
Answer c) Gram's decolorizer
Decolorizers act as the differential step of a differential staining process, removing the primary stain from one cell type while allowing it to remain in another.
Decolorizers act as the differential step of a differential staining process, removing the primary stain from one cell type while allowing it to remain in another.
19. Why is the crystal violet-iodine complex washed out of Gram-negative cells during decolorization?
- a) Gram's iodine fails to form a complex inside Gram-negative cells
- b) The decolorizer dissolves components of the outer membrane and cell membrane, making them more porous
- c) Gram-negative peptidoglycan becomes more tightly connected
- d) The safranin counter-stain displaces the complex from Gram-negative cells
Answer b) The decolorizer dissolves components of the outer membrane and cell membrane, making them more porous
The decolorizer interacts with the outer membrane and cell membrane, dissolving some of their components and making them more porous, so the complex washes out of the cell.
The decolorizer interacts with the outer membrane and cell membrane, dissolving some of their components and making them more porous, so the complex washes out of the cell.
20. A student prepares a smear that is far too thick. What error is this most likely to produce?
- a) Gram-negative cells falsely appearing Gram-positive
- b) Gram-positive cells falsely appearing Gram-negative
- c) Complete loss of all cells from the slide
- d) The counter-stain failing to enter any cells
Answer a) Gram-negative cells falsely appearing Gram-positive
If the smear is too thick, crystal violet may become trapped in the smear and not wash out during decolorization, causing Gram-negative cells to falsely appear Gram-positive.
If the smear is too thick, crystal violet may become trapped in the smear and not wash out during decolorization, causing Gram-negative cells to falsely appear Gram-positive.
21. What is the preferred age of a culture used for the Gram stain?
- a) 16-18 hours old
- b) 24-48 hours old
- c) At least 72 hours old
- d) One week old
Answer a) 16-18 hours old
Cultures should be less than 24 hours old, preferably 16-18 hours old, because aging cell walls weaken and Gram-positive cells may falsely appear Gram-negative.
Cultures should be less than 24 hours old, preferably 16-18 hours old, because aging cell walls weaken and Gram-positive cells may falsely appear Gram-negative.
22. Safranin enters both Gram-positive and Gram-negative cells. Why do Gram-positive cells still appear violet/purple at the end of the procedure?
- a) Safranin cannot bind to peptidoglycan
- b) The safranin is overshadowed by the darker crystal violet already present in the cell
- c) Safranin is rinsed away from Gram-positive cells
- d) Gram-positive cells convert safranin to crystal violet
Answer b) The safranin is overshadowed by the darker crystal violet already present in the cell
In Gram-positive cells the safranin is overshadowed by the darker crystal violet already present in the cell.
In Gram-positive cells the safranin is overshadowed by the darker crystal violet already present in the cell.
23. Knowing a bacterium's Gram stain result is clinically valuable primarily because Gram-positive and Gram-negative cells:
- a) Grow at different temperatures
- b) Have different susceptibilities to various antimicrobial drugs
- c) Produce different endospores
- d) Require different types of microscopes
Answer b) Have different susceptibilities to various antimicrobial drugs
Structural differences in the cell walls result in different susceptibilities to antimicrobial drugs, so the Gram stain result aids in selecting appropriate treatment.
Structural differences in the cell walls result in different susceptibilities to antimicrobial drugs, so the Gram stain result aids in selecting appropriate treatment.
24. The acid-fast staining procedure is known as the:
- a) Shaeffer-Fulton protocol
- b) Ziehl-Neelsen protocol
- c) Maneval protocol
- d) Gram protocol
Answer b) Ziehl-Neelsen protocol
The staining procedure used to stain acid-fast cells is known as the Ziehl-Neelsen protocol.
The staining procedure used to stain acid-fast cells is known as the Ziehl-Neelsen protocol.
25. Carbolfuchsin, the primary stain of the acid-fast procedure, is best described as:
- a) A dark red, lipid-soluble stain
- b) A green, water-soluble stain
- c) A blue, acidic stain
- d) A colorless mordant
Answer a) A dark red, lipid-soluble stain
Carbolfuchsin is a dark red stain that is lipid soluble, allowing it to penetrate the waxy mycolic acid in the cell wall.
Carbolfuchsin is a dark red stain that is lipid soluble, allowing it to penetrate the waxy mycolic acid in the cell wall.
26. Why do most aqueous stains fail to penetrate cells containing mycolic acids?
- a) Aqueous stains are too large to cross the cell wall
- b) Aqueous stains are polar and interact poorly with the non-polar mycolic acids
- c) Aqueous stains are positively charged and are repelled by the cell
- d) Mycolic acids chemically destroy aqueous stains
Answer b) Aqueous stains are polar and interact poorly with the non-polar mycolic acids
Aqueous stains are mixed with water, making them polar solutions that do not interact well with the non-polar nature of mycolic acids.
Aqueous stains are mixed with water, making them polar solutions that do not interact well with the non-polar nature of mycolic acids.
27. What is the purpose of applying heat at the same time the primary stain is added in the acid-fast procedure?
- a) It sterilizes the sample before handling
- b) It melts the waxy lipid, facilitating entry of the stain into the cell
- c) It evaporates excess stain from the slide
- d) It fixes the cells to the slide
Answer b) It melts the waxy lipid, facilitating entry of the stain into the cell
Heat melts the waxy lipid, thereby facilitating entry of the stain into the cell.
Heat melts the waxy lipid, thereby facilitating entry of the stain into the cell.
28. After the primary stain is applied with heat, the slide is removed from the heat and allowed to cool. Why is this step important?
- a) The wax solidifies, trapping the primary stain within cells containing mycolic acid
- b) Cooling allows the decolorizer to work more slowly
- c) Cooling causes the cells to adhere more firmly to the slide
- d) Cooling prevents the counter-stain from entering the cell
Answer a) The wax solidifies, trapping the primary stain within cells containing mycolic acid
The slide is removed from the heat and allowed to cool so the wax solidifies, trapping the primary stain in cells containing mycolic acid.
The slide is removed from the heat and allowed to cool so the wax solidifies, trapping the primary stain in cells containing mycolic acid.
29. Besides making cells difficult to stain, what do mycolic acids do for the bacteria that possess them? Select all that apply.
- a) Prevent the cells from desiccating
- b) Protect the cells from many chemical cleaners
- c) Allow the cells to form endospores
- d) Enable the cells to resist phagocytosis by forming a halo
Answers: a) Prevent the cells from desiccating; b) Protect the cells from many chemical cleaners
The waxes prevent the cells from desiccating and protect them from many chemical cleaners.
The waxes prevent the cells from desiccating and protect them from many chemical cleaners.
30. Why is methylene blue, the counter-stain, unable to color acid-fast cells?
- a) It is repelled by the mycolic acid
- b) It is washed away during the decolorization step
- c) It is too dilute to be visible
- d) It only binds to endospores
Answer a) It is repelled by the mycolic acid
Methylene blue cannot enter the cells of acid-fast bacteria because it is repelled by the mycolic acid.
Methylene blue cannot enter the cells of acid-fast bacteria because it is repelled by the mycolic acid.
31. The term acid-fast refers to the fact that these cells:
- a) Grow rapidly in acidic media
- b) Held fast to the primary stain despite treatment with the decolorizer
- c) Produce acid as a metabolic byproduct
- d) Are rapidly destroyed by acid-alcohol
Answer b) Held fast to the primary stain despite treatment with the decolorizer
These cells are referred to as acid-fast because they have held fast, or tightly, to the primary stain.
These cells are referred to as acid-fast because they have held fast, or tightly, to the primary stain.
32. Mycobacterium leprae, an organism detected using the acid-fast stain, is the causative agent of:
- a) Tuberculosis
- b) Leprosy
- c) Anthrax
- d) Tetanus
Answer b) Leprosy
Mycobacterium tuberculosis and Mycobacterium leprae cause tuberculosis and leprosy respectively.
Mycobacterium tuberculosis and Mycobacterium leprae cause tuberculosis and leprosy respectively.
33. The endospore staining method is known as the:
- a) Ziehl-Neelsen method
- b) Shaeffer-Fulton method
- c) Gram method
- d) Maneval method
Answer b) Shaeffer-Fulton method
The Shaeffer-Fulton method is used in this exercise to stain and visualize endospores.
The Shaeffer-Fulton method is used in this exercise to stain and visualize endospores.
34. During sporulation, the metabolically active cell that constructs the protective layers around a copy of the genetic material is called the:
- a) Endospore
- b) Vegetative cell (sporangium)
- c) Capsule
- d) Glycocalyx
Answer b) Vegetative cell (sporangium)
A vegetative cell, also called the sporangium, is a metabolically active cell that constructs several protective layers around a copy of the cell's genetic material.
A vegetative cell, also called the sporangium, is a metabolically active cell that constructs several protective layers around a copy of the cell's genetic material.
35. What is the function of an endospore?
- a) To increase the rate of bacterial reproduction
- b) To protect a copy of the genetic material in harsh environments
- c) To allow the cell to move through liquid media
- d) To prevent phagocytosis by host immune cells
Answer b) To protect a copy of the genetic material in harsh environments
Endospores protect a copy of the genetic material in harsh environments.
Endospores protect a copy of the genetic material in harsh environments.
36. Endospores are resistant to which of the following? Select all that apply.
- a) Extremes in temperature
- b) Radiation
- c) Chemicals
- d) Phagocytosis by host immune cells
Answers: a) Extremes in temperature; b) Radiation; c) Chemicals
Endospores are resistant to extremes in temperature, radiation, and chemicals. Resisting phagocytosis is a function of the capsule, not the endospore.
Endospores are resistant to extremes in temperature, radiation, and chemicals. Resisting phagocytosis is a function of the capsule, not the endospore.
37. How would an endospore appear on a slide that had been Gram stained rather than endospore stained?
- a) As a green structure inside the cell
- b) As a clear structure inside the cell
- c) As a dark purple structure inside the cell
- d) Endospores would not be visible at all
Answer b) As a clear structure inside the cell
Endospores are resistant to staining, so if present they appear as clear structures inside a cell after the Gram stain.
Endospores are resistant to staining, so if present they appear as clear structures inside a cell after the Gram stain.
38. Water serves as the decolorizing agent in the endospore stain because:
- a) Water is unable to penetrate the protective coat of the endospore, but washes the stain out of the vegetative cell
- b) Water chemically neutralizes malachite green
- c) Water dissolves the endospore coat
- d) Water is the only reagent safe to use with steam heat
Answer a) Water is unable to penetrate the protective coat of the endospore, but washes the stain out of the vegetative cell
Malachite green does not bind readily to the vegetative cell and washes out with water, while the water is unable to penetrate the protective coat of the endospore, so the endospore remains green.
Malachite green does not bind readily to the vegetative cell and washes out with water, while the water is unable to penetrate the protective coat of the endospore, so the endospore remains green.
39. Endospores are classified based on their location within the vegetative cell. Which of the following are recognized locations? Select all that apply.
- a) Central
- b) Terminal
- c) Subterminal
- d) Elliptical
Answers: a) Central; b) Terminal; c) Subterminal
There are three classifications based on location within the vegetative cell: central, terminal, and subterminal. Elliptical describes an endospore's shape, not its location.
There are three classifications based on location within the vegetative cell: central, terminal, and subterminal. Elliptical describes an endospore's shape, not its location.
40. Why must the Bacillus subtilis culture used for the endospore stain be at least 72 hours old?
- a) Older cells stain more readily with malachite green
- b) To ensure endospores have had an opportunity to form
- c) To allow the culture to become Gram-negative
- d) To reduce the number of vegetative cells to zero
Answer b) To ensure endospores have had an opportunity to form
A culture of Bacillus subtilis that is at least 72 hours old is used to ensure endospores have had an opportunity to form.
A culture of Bacillus subtilis that is at least 72 hours old is used to ensure endospores have had an opportunity to form.
41. Which of the following are endospore-forming pathogens? Select all that apply.
- a) Bacillus anthracis
- b) Clostridium tetani
- c) Clostridium botulinum
- d) Streptococcus pneumoniae
- e) Klebsiella pneumoniae
Answers: a) Bacillus anthracis; b) Clostridium tetani; c) Clostridium botulinum
Endospore-forming pathogens include Bacillus anthracis, Clostridium tetani, Clostridium botulinum, Clostridium perfringens, and Clostridium difficile. Streptococcus pneumoniae and Klebsiella pneumoniae are capsule formers.
Endospore-forming pathogens include Bacillus anthracis, Clostridium tetani, Clostridium botulinum, Clostridium perfringens, and Clostridium difficile. Streptococcus pneumoniae and Klebsiella pneumoniae are capsule formers.
42. A capsule is one type of bacterial:
- a) Glycocalyx
- b) Endospore
- c) Flagellum
- d) Mycolic acid
Answer a) Glycocalyx
Capsules are one type of bacterial glycocalyx.
Capsules are one type of bacterial glycocalyx.
43. Capsules are structures made of a combination of:
- a) Peptidoglycan and mycolic acids
- b) Polysaccharides and proteins
- c) Waxy lipids and agar
- d) Nucleic acids and phospholipids
Answer b) Polysaccharides and proteins
Capsules are made of a combination of polysaccharides and proteins, arranged to form a protective structure around the cell.
Capsules are made of a combination of polysaccharides and proteins, arranged to form a protective structure around the cell.
44. In addition to preventing phagocytosis and avoiding desiccation, capsules assist bacteria by:
- a) Aiding in the formation of biofilms by allowing cells to adhere to one another
- b) Increasing the rate of cell division
- c) Allowing the cell to survive boiling
- d) Producing endospores under stress
Answer a) Aiding in the formation of biofilms by allowing cells to adhere to one another
Capsules assist in the formation of biofilms by allowing cells to adhere to one another.
Capsules assist in the formation of biofilms by allowing cells to adhere to one another.
45. The capsule stain is described as a negative staining technique because:
- a) The capsule is stained a dark negative color
- b) An acidic dye is used that is repelled by the cell and stains the background instead
- c) The result is reported as either positive or negative
- d) No stain is applied to the slide at all
Answer b) An acidic dye is used that is repelled by the cell and stains the background instead
Capsule staining uses a negative staining technique: an acidic (anionic) stain is applied that is repelled by the negatively charged cell and stains the background instead.
Capsule staining uses a negative staining technique: an acidic (anionic) stain is applied that is repelled by the negatively charged cell and stains the background instead.
46. What is the role of Congo Red in the capsule stain procedure?
- a) It stains the bacterial cell pinkish red
- b) It stains the background surrounding the cells
- c) It stains the capsule directly
- d) It fixes the cells to the slide
Answer b) It stains the background surrounding the cells
Congo Red stains the background surrounding the cells because the negatively charged cell repels the negatively charged dye.
Congo Red stains the background surrounding the cells because the negatively charged cell repels the negatively charged dye.
47. Maneval's stain is a mixture of:
- a) Ethyl alcohol and hydrochloric acid
- b) Acetic acid and acid fuchsin
- c) Ethanol and acetone
- d) Malachite green and safranin
Answer b) Acetic acid and acid fuchsin
Maneval's stain is a mixture of acetic acid and acid fuchsin.
Maneval's stain is a mixture of acetic acid and acid fuchsin.
48. Which component of Maneval's stain causes the bacterial cells to appear pinkish red?
- a) Acetic acid
- b) Acid fuchsin
- c) Congo Red
- d) Crystal violet
Answer b) Acid fuchsin
The acid fuchsin is responsible for causing the bacterial cells to appear pinkish red.
The acid fuchsin is responsible for causing the bacterial cells to appear pinkish red.
49. Why does the Congo Red appear gray-blue at the end of the capsule stain procedure?
- a) The acidic pH of Maneval's stain causes the color change
- b) It is diluted by the deionized water rinse
- c) Heat fixation alters the pigment
- d) It reacts chemically with the capsule
Answer a) The acidic pH of Maneval's stain causes the color change
The acidic pH of Maneval's stain causes the Congo Red to appear gray-blue.
The acidic pH of Maneval's stain causes the Congo Red to appear gray-blue.
50. Following a properly performed capsule stain, the capsule is detected as:
- a) A clear halo located between the gray-blue background and the pinkish-red cell
- b) A bright green structure within the cell
- c) A dark blue ring staining the outer edge of the cell
- d) A red structure at the end of the cell
Answer a) A clear halo located between the gray-blue background and the pinkish-red cell
The capsule is indirectly detected as a clear halo located between the gray-blue background and the pinkish-red cell.
The capsule is indirectly detected as a clear halo located between the gray-blue background and the pinkish-red cell.
51. Heat fixation is omitted in the capsule stain procedure because capsules:
- a) May consist of up to 95% water, and heating causes dehydration, shrinkage, and distortion
- b) Are destroyed by contact with any glass surface
- c) Cannot adhere to a slide once heated
- d) Would be stained green rather than remaining clear
Answer a) May consist of up to 95% water, and heating causes dehydration, shrinkage, and distortion
Capsules may consist of up to 95% water. Heating the sample can cause the capsules to become dehydrated, resulting in shrinkage and distortion of the sample.
Capsules may consist of up to 95% water. Heating the sample can cause the capsules to become dehydrated, resulting in shrinkage and distortion of the sample.
52. Which of the following pathogens are known to form capsules? Select all that apply.
- a) Streptococcus pneumoniae
- b) Klebsiella pneumoniae
- c) Escherichia coli
- d) Clostridium tetani
Answers: a) Streptococcus pneumoniae; b) Klebsiella pneumoniae; c) Escherichia coli
Pathogens known to form capsules include Streptococcus pneumoniae, Klebsiella pneumoniae, and Escherichia coli. Clostridium tetani is an endospore-forming pathogen.
Pathogens known to form capsules include Streptococcus pneumoniae, Klebsiella pneumoniae, and Escherichia coli. Clostridium tetani is an endospore-forming pathogen.
This page titled 2.7.4: Multiple Choice / Multiple Select was last modified on Sat, 25 Jul 2026 03:43:05 GMT and is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Sherry Smith.
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