BIOD 151 Module 3 Exam Answer Key
(Portage learning)
1. Gram staining - ANSWER the observations that different types of bacteria
react differently to various dyes. This differentiation, based on color, divided
bacteria into two categories: Gram-positive or Gram-negative
2. Gram-positive - ANSWER Thick peptidoglycan layer, Gram-positive cells
appear purple
3. Gram-negative - ANSWER Thin peptidoglycan layer, Gram-negative
bacteria will initially retain the crystal violet dye. Gram-negative bacteria
now retain a pink color.
4. Differential staining - ANSWER a generalized term used for any staining
technique that separates specimens into further subgroups. This process most
often utilizes at least two dyes.
5. Heat fixation - ANSWER samples are added to a glass slide and then passed
through a flame until all liquid in the sample has been removed
6. Chemical fixation - ANSWER include the use of paraformaldehyde, ethanol,
or methanol. Although these processes fix the sample to the slide, it also
kills the microorganism. As such, characteristics related to motility
(movement) are not possible.
,7. Wet mount - ANSWER a basic form of sample preparation for viewing live
samples. A small liquid culture (usually just a drop) containing a
microorganism of interest is prepared, added to a slide, and then covered
with a glass coverslip. are used to observe the motility and behavior of an
organism.
8. What is a coverslip? - ANSWER coverslip is present to both protect the
objective and the specimen while also holding the microorganism in place.
9. Simple staining - ANSWER uses a solution of a positively charged dye, such
as methylene blue, crystal violet, safranin, or fuchsin, to bind to and stain the
negatively charged membrane of the microorganism. This simple technique
is often used to quickly observe the size, shape, and arrangement of cells.
10.Negative staining - ANSWER Creates "capsule effect", Acidic dyes
(anionic) that are repelled by the negative surface charge of a cell. Instead of
staining the microorganism, you stain everything except the microorganism.
By applying the dark stain nigrosin (or India ink) to a sample, its negative
charge is repelled by the negatively charged membrane, resulting in a sharp
contrast between the unstained specimen and the now dark background. Cell
remains colorless, but background is stained to give a contrast
11.Acid-fast staining (also known as the Ziehl-Neelsen stain) - ANSWER a
differential stain used to identify bacterial stains showing a high degree of
resistance to decolorization.
Differential Stains: Acid-fast
Stains: Mycobacterium and Nocardia
12.For cells that resist decolorization> - ANSWER Primary dye: Carbolfuchsin
(red)
Counterstain: Methylene (Blue)
, Cells remain colorless but background is stained to give a contrast
Tuberculosis, leprosy, lung and skin infections
13.Giemsa - ANSWER a differential stain, Combined with Wright's stain
(stains blood cells), the resulting combinatorial stain can be applied to blood
smears to determine the presence (or absence) of pathogenic bacteria —
human (blood) cells appear purple, and bacterial cells appear as pink. This
staining is most often used for the diagnosis of malaria as well as other
blood parasites.
14.Gram Stain Steps - ANSWER Heat Fixation
Primary Stain
Mordant
Decolorizing agent
Counterstain
15.Types of Differential stains - ANSWER Gram, acid-fast, endospore,
hematoxylin, eosin staining
16.Types of Special Stains - ANSWER Negative stains, flagellar stains, and
fluorescent stains
17.Types of simple stains - ANSWER crystal violet, safranin, fuchsin,
methylene blue
18.Chemistry of Staining - ANSWER stains are salts, which break down into
positively and negatively charged ions
(Portage learning)
1. Gram staining - ANSWER the observations that different types of bacteria
react differently to various dyes. This differentiation, based on color, divided
bacteria into two categories: Gram-positive or Gram-negative
2. Gram-positive - ANSWER Thick peptidoglycan layer, Gram-positive cells
appear purple
3. Gram-negative - ANSWER Thin peptidoglycan layer, Gram-negative
bacteria will initially retain the crystal violet dye. Gram-negative bacteria
now retain a pink color.
4. Differential staining - ANSWER a generalized term used for any staining
technique that separates specimens into further subgroups. This process most
often utilizes at least two dyes.
5. Heat fixation - ANSWER samples are added to a glass slide and then passed
through a flame until all liquid in the sample has been removed
6. Chemical fixation - ANSWER include the use of paraformaldehyde, ethanol,
or methanol. Although these processes fix the sample to the slide, it also
kills the microorganism. As such, characteristics related to motility
(movement) are not possible.
,7. Wet mount - ANSWER a basic form of sample preparation for viewing live
samples. A small liquid culture (usually just a drop) containing a
microorganism of interest is prepared, added to a slide, and then covered
with a glass coverslip. are used to observe the motility and behavior of an
organism.
8. What is a coverslip? - ANSWER coverslip is present to both protect the
objective and the specimen while also holding the microorganism in place.
9. Simple staining - ANSWER uses a solution of a positively charged dye, such
as methylene blue, crystal violet, safranin, or fuchsin, to bind to and stain the
negatively charged membrane of the microorganism. This simple technique
is often used to quickly observe the size, shape, and arrangement of cells.
10.Negative staining - ANSWER Creates "capsule effect", Acidic dyes
(anionic) that are repelled by the negative surface charge of a cell. Instead of
staining the microorganism, you stain everything except the microorganism.
By applying the dark stain nigrosin (or India ink) to a sample, its negative
charge is repelled by the negatively charged membrane, resulting in a sharp
contrast between the unstained specimen and the now dark background. Cell
remains colorless, but background is stained to give a contrast
11.Acid-fast staining (also known as the Ziehl-Neelsen stain) - ANSWER a
differential stain used to identify bacterial stains showing a high degree of
resistance to decolorization.
Differential Stains: Acid-fast
Stains: Mycobacterium and Nocardia
12.For cells that resist decolorization> - ANSWER Primary dye: Carbolfuchsin
(red)
Counterstain: Methylene (Blue)
, Cells remain colorless but background is stained to give a contrast
Tuberculosis, leprosy, lung and skin infections
13.Giemsa - ANSWER a differential stain, Combined with Wright's stain
(stains blood cells), the resulting combinatorial stain can be applied to blood
smears to determine the presence (or absence) of pathogenic bacteria —
human (blood) cells appear purple, and bacterial cells appear as pink. This
staining is most often used for the diagnosis of malaria as well as other
blood parasites.
14.Gram Stain Steps - ANSWER Heat Fixation
Primary Stain
Mordant
Decolorizing agent
Counterstain
15.Types of Differential stains - ANSWER Gram, acid-fast, endospore,
hematoxylin, eosin staining
16.Types of Special Stains - ANSWER Negative stains, flagellar stains, and
fluorescent stains
17.Types of simple stains - ANSWER crystal violet, safranin, fuchsin,
methylene blue
18.Chemistry of Staining - ANSWER stains are salts, which break down into
positively and negatively charged ions
