Microbiology - Lab 5-6

Who developed the Gram staining technique?

• Hans Christian Gram

• Louis Pasteur

• Robert Koch

• Alexander Fleming

What is the purpose of decolorizing with ethanol in the Gram stain?

• To help visualize capsule structures.

• To stain all bacteria purple.

• Dissolves the outer membrane of the Gram-negative bacteria, and
  the thin peptidoglycan layer cannot retain the CV-I complex

• To differentiate between Gram-positive and Gram-negative bacteria.

• To create a complex with crystal violet.

Explain the significance of safranin in Gram staining.

• Decolorizer in gram staining.

• Gram-positive bacteria are already stained and are not affected by safranin. Gives gram-negative bacteria a pinkish red color.

• To differentiate between Gram-positive and Gram-negative bacteria.

• To create a complex with crystal violet.

What is the function of the mordant in the Gram stain?

• It forms a complex with crystal violet within the peptidoglycan.

• It dissolves the outer membrane of the Gram-negative bacteria.

• It dehydrates the peptidoglycan layer of Gram-positive bacteria.

• It gives color to the Gram-negative cells.

The Gram stain is a staining method used in microbiology to differentiate bacteria based on their:

• Cell arrangement

• Size

• Shape

• Cell wall characteristics

What is the purpose of skipping the heat fixation step in the capsule stain procedure?

• Capsule are fragile and can be destroyed with heating.

• Heat fixation is unnecessary because organisms with capsules naturally adhere to the slide.

• Capsule will appear too dark if heated

• Capsule are converted to slime layers if heated

• Heat fixation is unnecessary in capsule staining because the organisms are harmless.

What is the purpose of Gram staining?

• To identify and classify bacteria

• To stain the capsule of bacteria

• To stain the flagella of bacteria

• To stain the endospores of bacteria

Which type of bacteria retains the purple color after Gram staining?

• Gram-positive bacteria

• Gram-negative bacteria

• Capsulated bacteria

• Bacteria containing mycolic acid

What is the purpose of capsule staining?

• To stain the bacterium and the background but not the capsule

• To identify and classify bacteria

• To stain the flagella of bacteria

• To permanently stain endospores

Which bacterial structure allows bacteria to move and run away from phagocytosis?

• Flagella

• Capsule

• Peptidoglycan

• Lipopolysaccharide