Deck 2: Observing the Microbial Cell

Question 1

If a glass slide was submerged in a beaker of immersion oil, the slide would be:

A) undetectable
B) brighter than its surroundings
C) darker than its surroundings
D) fluorescent
E) stained

Answer 1

A

Question 2

Increasing the refractive index of the medium between the object and the objective lens increases:

A) refraction
B) reflection
C) magnification
D) resolution
E) wavelength

Answer 2

D

Question 3

In a proper Gram stain, positive cells are stained by:

A) crystal violet only
B) safranin only
C) both crystal violet and safranin
D) neither crystal violet nor safranin
E) not enough information has been provided to know

Answer 3

C

Question 4

Which of these arranges the steps of the Gram stain into the correct order?

A) iodine $\rarr$ crystal violet $\rarr$ decolorizer $\rarr$ safranin
B) safranin $\rarr$ decolorizer $\rarr$ crystal violet $\rarr$ iodine
C) crystal violet $\rarr$ decolorizer $\rarr$ iodine $\rarr$ safranin
D) crystal violet $\rarr$ decolorizer $\rarr$ safranin $\rarr$ iodine
E) crystal violet $\rarr$ iodine $\rarr$ decolorizer $\rarr$ safranin

Question 5

As lens strength increases, the light cone __________ and the lens must be __________ the object.

A) narrows; nearer to
B) narrows; farther from
C) widens; nearer to
D) widens; farther from
E) widens; touching

Question 6

Resolution is the smallest distance by which two objects can be __________ and still be __________.

A) magnified; seen
B) separated; distinguished
C) magnified; separated
D) distinguished; separated
E) magnified; distinguished

Question 7

Staining helps to visualize bacteria by:

A) increasing the size of the cells
B) increasing the motility of the cells
C) increasing the contrast of the image
D) increasing the magnification of the image
E) increasing the aberration of the image

Question 8

A ball-shaped microbe is referred to as a:

A) bacillus
B) coccus
C) vibrio
D) strepto
E) spirochete

Question 9

A(n) __________ acts to vary the diameter of the light column in a light microscope.

A) condenser
B) objective
C) ocular
D) diaphragm
E) lens

Question 10

Wavelength interference results in small observed objects (like bacteria) being surrounded by:

A) a capsule
B) a membrane
C) an Airy disk
D) a dark field
E) a cell wall

Question 11

Malachite green is commonly used to stain:

A) eukaryotic cells
B) Gram-negative cells
C) Gram-positive cells
D) bacterial endospores
E) acid-fast cells

Question 12

Which of these series arranges microbes from smallest to largest?

A) virus $\rarr$ bacterium $\rarr$ red blood cell $\rarr$ paramecium
B) virus $\rarr$ red blood cell $\rarr$ bacterium $\rarr$ paramecium
C) bacterium $\rarr$ virus $\rarr$ paramecium $\rarr$ red blood cell
D) bacterium $\rarr$ virus $\rarr$ red blood cell $\rarr$ paramecium
E) paramecium $\rarr$ red blood cell $\rarr$ bacterium $\rarr$ virus

Question 13

The part of the human eye that is most involved in resolving an image is the:

A) iris
B) lens
C) optic nerve
D) retina
E) cornea

Question 14

Who proved that stomach ulcers are caused by a bacterium?

A) Hooke
B) Marshall
C) Gram
D) Jenner
E) van Leeuwenhoek

Question 15

When two waves are out of phase by __________ wavelength, they produce destructive interference, canceling each other's amplitude and resulting in contrast in the image.

A) one-tenth of a
B) one-eighth of a
C) one-quarter of a
D) one-half of a
E) one

Question 16

What would happen if a lens had the same refractive index as air?

A) Light would not pass through the lens.
B) The image would be magnified more than with a glass lens.
C) The image would be magnified, but the resolution would be less than with a glass lens.
D) The image would be magnified, and the resolution would be greater than with a glass lens.
E) The image would not be magnified.

Question 17

The highest useful magnification for a light microscope is about:

A) 100X
B) 1,000X
C) 10,000X
D) 100,000X
E) 1,000,000X

Question 18

When Gram stained, most eukaryotes appear:

A) colorless
B) purple
C) pink
D) green
E) black

Question 19

What is the most important property that enables a lens to magnify an image?

A) absorption
B) fluorescence
C) reflection
D) refraction
E) scattering

Question 20

The heating of water when exposed to light is primarily due to:

A) reflection
B) refraction
C) absorption
D) scattering
E) fluorescence

Question 21

What is the total magnification of a light microscope when using a 25X ocular and 40X objective lens?

A) 15X
B) 65X
C) 400X
D) 1,000X
E) 1,200X

Question 22

In which type of microscopy do dust particles interfere the most?

A) bright-field microscopy
B) dark-field microscopy
C) phase-contrast microscopy
D) interference microscopy
E) fluorescence microscopy

Question 23

Which of the following can be used to localize proteins in a microbial cell?

A) DAPI and immunofluorescence
B) acridine orange and green fluorescent protein (GFP) fusions
C) DAPI and acridine orange
D) GFP fusions and immunofluorescence
E) DAPI and GFP fusions

Question 24

Which of the following would be best suited to observe the motility of microbial cells?

A) Gram stain
B) nuclear magnetic resonance
C) scanning electron microscopy
D) negative stain
E) phase-contrast microscopy

Question 25

The knife used to cut embedded specimens for observation by transmission electron microscopy is called a:

A) crystallographer
B) microtome
C) grid
D) polymer
E) scalpel

Question 26

A useful application of dark-field optics is the study of bacterial:

A) motility
B) surfaces
C) interiors
D) shape
E) structure

Question 27

Which of the following is best visualized using a negative stain?

A) Gram-negative cell wall
B) acid-fast cell wall
C) capsule
D) endospores
E) flagella

Question 28

What is the best explanation for a Gram-positive bacterium appearing pink after performing a Gram stain?

A) The crystal violet was left on for too long.
B) The iodine was left on for too long.
C) The decolorizer was left on for too long.
D) The safranin was left on for too long.
E) The stain was properly performed.

Question 29

The aromatic groups of the fluorophore DAPI associate exclusively with the:

A) cell wall
B) base pairs of DNA
C) flagella
D) cell membrane
E) pili

Question 30

Which form of microscopy is used with DNA microarrays to observe differences in gene expression?

A) light microscopy
B) atomic force microscopy
C) scanning electron microscopy
D) transmission electron microscopy
E) confocal fluorescence microscopy

Question 31

What is the best explanation for a Gram-negative bacterium appearing purple after performing a Gram stain?

A) The safranin was not applied.
B) The decolorizer was not applied.
C) The iodine was not applied.
D) The crystal violet was not applied.
E) The stain was properly performed.

Question 32

Which two components of the Gram stain form a complex that is retained by Gram-positive cells?

A) crystal violet and iodine
B) safranin and iodine
C) crystal violet and safranin
D) alcohol and safranin
E) alcohol and iodine

Question 33

A fluorophore used in fluorescence microscopy that absorbs light at 260 nm would most likely fluoresce at:

A) 100 nm
B) 200 nm
C) 260 nm
D) 400 nm
E) 800 nm

Question 34

Fluorescence microscopy using labeled antibodies is referred to as:

A) immunofluorescence
B) autofluorescence
C) confocal microscopy
D) phase-contrast microscopy
E) dark-field microscopy

Question 35

Which of these techniques can be used to localize the DNA sequence at the origin of replication in a bacterial cell?

A) fluorescence microscopy
B) phase contrast
C) X-ray diffraction
D) atomic force microscopy
E) cryo-EM

Question 36

The fluorophore DAPI specifically binds:

A) the cytoplasm
B) the cell wall
C) protein
D) RNA
E) DNA

Question 37

Which of the following techniques are based upon wave interference?

A) X-ray diffraction and phase contrast microscopy
B) phase contrast and dark-field microscopy
C) bright-field and dark-field microscopy
D) X-ray diffraction and atomic force microscopy
E) scanning and transmission electron microscopy

Question 38

DAPI is a dye that is commonly used in _____________ microscopy.

A) bright-field
B) dark-field
C) phase contrast
D) confocal
E) fluorescence

Question 39

Which of these numeric aperture and light combinations would give the best resolution?

A) numeric aperture = 0.8, wavelength = 600 nm
B) numeric aperture = 0.8, wavelength = 500 nm
C) numeric aperture = 1.0, wavelength = 700 nm
D) numeric aperture = 1.0, wavelength = 600 nm
E) numeric aperture = 0.8, wavelength = 400 nm

Question 40

Atomic force microscopy measures __________ between a probe and an object to map the three-dimensional topography of a cell.

A) hydrogen bonds
B) covalent interactions
C) van der Waals forces
D) pH changes
E) magnetic interactions

Question 41

Which of these techniques would provide the best resolution of an enzyme's structure?

A) scanning electron microscopy
B) transmission electron microscopy
C) cryo-EM
D) X-ray diffraction analysis
E) atomic force microscopy

Question 42

Unlike transmission electron microscopy, cryo-electron microscopy:

A) requires making thin slices of the sample to be viewed
B) does not require staining with heavy metals
C) may be used to view living tissues
D) uses a weaker electron beam
E) can provide a color image of the microbial cell

Question 43

List and describe three common shapes of bacteria.

Question 44

Transmission electron microscopy commonly has a resolution of __________ times the highest resolution possible for light microscopy.

A) 10
B) 100
C) 1,000
D) 10,000
E) 1,000,000

Question 45

Which of the following techniques can visualize bacteria without focusing electromagnetic radiation?

A) cryo-electron microscopy
B) phase-contrast microscopy
C) dark-field microscopy
D) atomic force microscopy
E) X-ray diffraction

Question 46

The digitally combined images of cryo-EM can achieve resolution comparable to that of:

A) scanning electron microscopy
B) transmission electron microscopy
C) interference microscopy
D) X-ray crystallography
E) dark-field microscopy

Question 47

A microscopic structure that is interpreted incorrectly is a/an:

A) microtome
B) crystal
C) shadow
D) antibody
E) artifact

Question 48

Which of the following would be most appropriate to visualize viral particles being assembled inside an infected bacterial cell?

A) dark-field microscopy
B) atomic force microscopy
C) fluorescence microscopy
D) scanning electron microscopy
E) transmission electron microscopy

Question 49

What color are Gram-positive and Gram-negative cells when properly Gram stained? For each step of the Gram stain procedure, predict the colors of a Gram-positive or Gram-negative cell if that step were omitted during staining. Explain your reasoning.

Question 50

Why do some bacteria appear purple after being Gram stained, while others appear pink?

Question 51

Describe three conditions that are necessary for electromagnetic radiation to resolve an object.

Question 52

The spots recorded on film during X-ray diffraction analyses are due to:

A) artifacts
B) scattering
C) wave interference
D) absorption
E) fluorescence

Question 53

Are all bacilli Bacillus? Explain.

Question 54

Compare and contrast the radiation sources, lenses, and image-capturing devices used in light microscopy and transmission electron microscopy.

Question 55

Compare and contrast a simple stain (like methylene blue) with the Gram stain. What information about a microbial sample can be collected with each?

Question 56

If your eyes had photoreceptors packed as closely as an eagle's (about eight times greater than humans), would you be able to resolve a virus (100 nm in size) using a light microscope? Why or why not?

Question 57

List and briefly describe four ways that light interacts with objects.

Question 58

List three different differential stains used in microbiology. What can be detected with each?

Question 59

Microbes were detected long before the invention of the microscope. How could this be?

Question 60

Which type of microscopy is particularly useful to study the surfaces of live bacteria?

A) atomic force
B) scanning electron
C) transmission electron
D) dark-field
E) bright-field

Question 61

Why are stains used in microscopy? Compare and contrast the stains used in light versus electron microscopy.

Question 62

Define a fluorophore and give three examples of how it can be used to label cells.

Question 63

Name two types of microscopy that are suitable for directly studying bacterial motility. What interaction of light with the microbe is most important for each of these techniques?

Question 64

Most electron micrographs in microbiology textbooks are in color. Is this normal for an electron micrograph? Why or why not?

Question 65

Describe three methods of sample preparation for electron microscopy. Which method would cause the fewest artifacts? Why?

Question 66

Archaea and Bacteria differ in the genetic sequences of their ribosomal RNA genes. How can this difference be used to microscopically differentiate between members of these domains?

Question 67

If you are interested in studying the localization of a protein in a bacterial cell, what techniques would provide you with the best information?

Question 68

Give a few reasons why living organisms may not be observed by transmission electron microscopy (TEM) or scanning electron microscopy (SEM).