MICROBIOLOGY 211 (CHAPTER 3) QUESTIONS WITH COMPLETE SOLUTIONS 100% VERIFIED|
LATEST UPDATE GRADED A+
We can we compensate for the lack of contrast between a cell and its background? Special
lenses (phase-contrast microscope) or by using dyes on the sample.
List the names of the four types of visible-light microscopes. Bright-field, dark-field, phase-
contrast and interference microscopy.
What are basic stains, what do they do? Name four basic stains. Stains that are positively
charged that bind to the microbial cell membrane
Methylene blue, safranin, crystal violet and malachite green.
What is another name for a negative stain? What do these stains do? And name two. Acidic
(anionic). These stains are the same charge as the cell membrane and are repelled by it so they
show the cell in relief. India ink and nigrosin.
What is the concept of the differential stain? Give examples. -They distinguish different
features of the microbial cell or they accentuate microbes based on a cellular feature.
-Gram positive cells have a thick peptidoglycan outer layer while gram negative have a thin
peptidoglycan layer under an outer membrane.
-Endospore stains use heat to force stain into cells and distinguish stained spore from the
vegetative cells.
-Flagellar stains build up stain on the flagella to increase their diameter and bring them into
resolution range of the microscope.
How does colony morphology of the Streptococci differ from that of the Staphylococci?
Streptococci divide at right angles to one plane and remain attached forming chains of
different lengths while Staphylococci divide along a number of planes and form bunches.
, What is a very simple description of an antibody? A four protein molecule whose quaternary
structure produces a Y-shaped molecule that has the ability to recognize and bind to a
particular molecule.
What is a good sample to use the direct fluorescence assay on?
What are the exceptions. When ordinary stains are ineffective or the suspected organism
cannot be cultured
What kind of assay is the Streptococcus dipstick test that we discussed? Direct antigen
testing.
What are the Five I's of microbial cultivation in order of operation? Inoculation, incubation,
isolation, inspection, identification
What are the steps involved in inoculation? The sample is transferred from the transport
medium into a sterile liquid medium that contains appropriate nutrients to sustain growth of
the organism. A small sample of this is used for re-inoculating a liquid medium or for spreading
on solid agar plates.
What is involved in incubation? An incubator is a cabinet that provides constant heating and
atmospheric gas mixtures optimal for the growth of the organisms in the culture.
How is isolation achieved? Spread plate or streak plate method produces separate colonies
which are piles of cells that have been separated from each other in the streaking process and
allowed to divide until they produce a visible colony.
What does inspection involve? -Macroscopic inspection involves observing the colonies for
size, color and texture.
LATEST UPDATE GRADED A+
We can we compensate for the lack of contrast between a cell and its background? Special
lenses (phase-contrast microscope) or by using dyes on the sample.
List the names of the four types of visible-light microscopes. Bright-field, dark-field, phase-
contrast and interference microscopy.
What are basic stains, what do they do? Name four basic stains. Stains that are positively
charged that bind to the microbial cell membrane
Methylene blue, safranin, crystal violet and malachite green.
What is another name for a negative stain? What do these stains do? And name two. Acidic
(anionic). These stains are the same charge as the cell membrane and are repelled by it so they
show the cell in relief. India ink and nigrosin.
What is the concept of the differential stain? Give examples. -They distinguish different
features of the microbial cell or they accentuate microbes based on a cellular feature.
-Gram positive cells have a thick peptidoglycan outer layer while gram negative have a thin
peptidoglycan layer under an outer membrane.
-Endospore stains use heat to force stain into cells and distinguish stained spore from the
vegetative cells.
-Flagellar stains build up stain on the flagella to increase their diameter and bring them into
resolution range of the microscope.
How does colony morphology of the Streptococci differ from that of the Staphylococci?
Streptococci divide at right angles to one plane and remain attached forming chains of
different lengths while Staphylococci divide along a number of planes and form bunches.
, What is a very simple description of an antibody? A four protein molecule whose quaternary
structure produces a Y-shaped molecule that has the ability to recognize and bind to a
particular molecule.
What is a good sample to use the direct fluorescence assay on?
What are the exceptions. When ordinary stains are ineffective or the suspected organism
cannot be cultured
What kind of assay is the Streptococcus dipstick test that we discussed? Direct antigen
testing.
What are the Five I's of microbial cultivation in order of operation? Inoculation, incubation,
isolation, inspection, identification
What are the steps involved in inoculation? The sample is transferred from the transport
medium into a sterile liquid medium that contains appropriate nutrients to sustain growth of
the organism. A small sample of this is used for re-inoculating a liquid medium or for spreading
on solid agar plates.
What is involved in incubation? An incubator is a cabinet that provides constant heating and
atmospheric gas mixtures optimal for the growth of the organisms in the culture.
How is isolation achieved? Spread plate or streak plate method produces separate colonies
which are piles of cells that have been separated from each other in the streaking process and
allowed to divide until they produce a visible colony.
What does inspection involve? -Macroscopic inspection involves observing the colonies for
size, color and texture.
