micro lab exam 1

Predict the result of the following “mistake” made when performing a Gram stain. Reversal of crystal violet and safranin stains

A.  all cells would be transparent
B. gram negative cells would look like gram positives
C. all cells would appear gram negative
D. all cells would appear gram positive

What is the name of the primary stain used in a gram stain?

A. carbolfusion
B. crystal violet
C. methylene blue
D. safranin

What is a negative stain?

A. a stain that stains the endospore instead of the cell
B. a stain that fades away after a few days
C. a stain that colors the background rather than the cell
D. a stain that reverses the crytal violet and safranin applications

When is it appropriate to ask the laboratory to perform an acid-fast stain?

A. when an acid fast organism is suspected
B. every time you run tests just in case
C. when the suspected organism is a spirochete
D. when you think the bacterium might have teichoic acid in its cell wall

What is the function of the iodine in a gram stain?

A. it removes the primary stain
B. it removes the safranin
C. it holds the primary stain in gram positives
D. it keeps the flagellum from falling off

What is the advantage of the gram stain over the simple stain?

A. it allows us to see the flagellum
B.  it identifies the cell wall structure
C. it colors the entire cell
D. it colors all cells the same

Predict the result of the following “mistake” made when performing a Gram stain.

Failure to apply the counterstain

A. some cells would be transparent while some would appear gram-positive
B. all cells would appear to have endospores
C. all cells would appear gram positive
D. all cells would appear gram negative

Predict the result of the following “mistake” made when performing a Gram stain. 

Failure to apply the alcohol solution

A. all cells would appear gram positive
B. all cells would appear gram negative
C. all cells would appear to have endospores
D. all cells would be transparent

What is the purpose of the alcohol solution in a gram stain?

A. it removes the safranin
B. it removes the primary stain
C. it keeps the flagellum from falling off
D. it holds the primary stain in gram positives

In the acid-fast staining procedure, why is carbolfuchsin used as a primary stain?

A. it washes away with 2% acid-alcohol
B. it can penetrate the waxy-lipid cell wall
C. it contains a mordant to hold it inside the cell
D. it stains acid fast cells blue

Name the three locations that a spore may be found within a vegetative cell. (Select all that apply)

A. terminal
B. central
C. subterminal

Why is a Gram stain not an adequate substitute for an acid-fast stain?

gram staining cannot penetrate cell walls with mycolic acid in them

What does the mordant do in a flagella stain?

it makes the flagellum thick enough to see

What is a pure culture?

A: colony that contains only one species of bacterium