Question 1

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

Accepted Answer

Detection is the ability to observe the presence of an object, such as when we detect a group of bacteria in a culture tube or growing on a surface such as a food product. Even though we can detect the group, we cannot resolve individual cells without the magnification afforded by microscopes.

Question 2

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

Accepted Answer

Gram-negative cells have a few layers of peptidoglycan cell wall and an outer lipopolysaccharide membrane. Gram-positive organisms have several layers of peptidoglycan and no outer membrane. The multiple layers of peptidoglycan retain the crystal violet-iodine complex, so appear purple. Gram-negative cells do not retain the crystal violet because there are few layers of peptidoglycan and the outer membrane is disrupted by the decolorizer.

Question 3

Fluorescence microscopy using labeled antibodies is referred to as

Accepted Answer

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

Question 4

Malachite green is commonly used to stain

Accepted Answer

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

Question 5

Are all bacilli Bacillus? Explain.

Accepted Answer

No. Bacillus refers to a particular genu

Question 6

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.

Accepted Answer

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

Question 7

One advantage of a wet mount is

Accepted Answer

A)  low contrast. 
B)  that the organism is still. 
C)  viewing in a natural state. 
D)  high contrast. 
E)  that the sample does not overheat. 
A)  low contrast. 
B)  that the organism is still. 
C)  viewing in a natural state. 
D)  high contrast. 
E)  that the sample does not overheat.

Question 8

Cryo-electron microscopy (cryo-EM) is differentiated from transmission electron microscopy because it

Accepted Answer

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. 
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 9

List and describe three common shapes of bacteria.

Accepted Answer

Bacilli (bacillus in the singu

Question 10

Using the figure below, explain how the visualization of molecules occurs through X-ray crystallography.

Accepted Answer

The X-ray beam focuses on a crystal and

Question 11

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

Accepted Answer

A fluorophore is a fluorescent molecule

Question 12

If aqueous cytoplasm was submerged in a beaker of immersion oil, the slide would be

Accepted Answer

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

Question 13

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

Accepted Answer

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

Question 14

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

Accepted Answer

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

Question 15

Which of the following is an advantage of using chemical imaging microscopy?

Accepted Answer

A)  observing an organism in its living environment 
B)  displaying plankton 
C)  measuring pH within a cell 
D)  showing distribution of chemicals in a cell 
E)  pinpointing a protein location 
A)  observing an organism in its living environment 
B)  displaying plankton 
C)  measuring pH within a cell 
D)  showing distribution of chemicals in a cell 
E)  pinpointing a protein location

Question 16

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

Accepted Answer

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

Question 17

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

Accepted Answer

Both staining procedures colorize bacter

Question 18

Fluorescent microscopy that absorbs light at 260m would MOST likely fluoresce at

Accepted Answer

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

Question 19

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

Accepted Answer

The radiation source for light microscop

Question 20

Which type of microscopy is used to identify the 3-D structure of biofilms?

Accepted Answer

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

Exam 2: Observing the Microbial Cell

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

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

Fluorescence microscopy using labeled antibodies is referred to as

Malachite green is commonly used to stain

Are all bacilli Bacillus? Explain.

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.

One advantage of a wet mount is

Cryo-electron microscopy (cryo-EM) is differentiated from transmission electron microscopy because it

List and describe three common shapes of bacteria.

Using the figure below, explain how the visualization of molecules occurs through X-ray crystallography.

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

If aqueous cytoplasm was submerged in a beaker of immersion oil, the slide would be

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

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

Which of the following is an advantage of using chemical imaging microscopy?

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

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

Fluorescent microscopy that absorbs light at 260m would MOST likely fluoresce at

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

Which type of microscopy is used to identify the 3-D structure of biofilms?

Microbial Life: Origin and Discovery

Cell Structure and Function

Bacterial Culture, Growth, and Development

Environmental Influences and Control of Microbial Growth

Viruses

Genomes and Chromosomes

Transcription, Translation, and Bioinformatics

Gene Transfer, Mutations, and Genome Evolution

Molecular Regulation

Viral Molecular Biology

Biotechniques and Synthetic Biology

Energetics and Catabolism

Electron Flow in Organotrophy, Lithotrophy, and Phototrophy

Biosynthesis

Food and Industrial Microbiology

Origins and Evolution

Bacterial Diversity

Archaeal Diversity

Eukaryotic Diversity

Microbial Ecology

Microbes in Global Elemental Cycles

Human Microbiota and Innate Immunity

The Adaptive Immune Response

Microbial Pathogenesis

Microbial Diseases

Antimicrobial Therapy

Clinical Microbiology and Epidemiology

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