Gram Stain Flashcards
What is the primary purpose of the Gram stain?
To differentiate between Gram-positive and Gram-negative bacteria.
True or False: Gram-positive bacteria have a thick peptidoglycan layer.
True
What color do Gram-positive bacteria appear after a Gram stain?
Purple
What color do Gram-negative bacteria appear after a Gram stain?
Pink
Fill in the blank: The Gram stain involves the use of a _______ to fix the bacteria onto the slide.
Heat
What is the first reagent used in the Gram staining procedure?
Crystal violet
What is the second reagent applied in the Gram stain process?
Iodine
What is the role of iodine in the Gram staining procedure?
It acts as a mordant to form a complex with crystal violet.
What is the decolorizing agent used in the Gram stain?
Alcohol or acetone
True or False: All bacteria can be classified as either Gram-positive or Gram-negative.
False
What is the counterstain used in the Gram staining process?
Safranin
What is the significance of the Gram stain in clinical microbiology?
It helps guide antibiotic treatment and informs about the type of bacteria present.
Short answer: Describe the appearance of Gram-negative bacteria under a microscope after staining.
They appear pink and are often rod-shaped or cocci.
What type of bacteria typically have an outer membrane?
Gram-negative bacteria
Multiple choice: Which of the following is NOT a step in the Gram staining process? A) Crystal violet B) Iodine C) Heat fixation D) Glucose
D) Glucose
Fill in the blank: The Gram stain is named after the Danish bacteriologist _______.
Hans Christian Gram
True or False: The Gram stain can be used to identify mycobacteria.
False
What type of microscopy is typically used to observe the results of a Gram stain?
Light microscopy
What does a Gram stain reveal about bacterial cell wall structure?
It indicates the thickness of the peptidoglycan layer.
Short answer: Why is it important to use fresh cultures for Gram staining?
Fresh cultures provide accurate results as older cultures may lose their Gram characteristics.
Multiple choice: Which bacteria are typically resistant to Gram staining? A) Mycobacteria B) Streptococci C) Escherichia coli D) Staphylococci
A) Mycobacteria
What is the main limitation of the Gram stain?
It does not differentiate between all bacterial species.
Fill in the blank: Gram-negative bacteria are generally more resistant to _______ compared to Gram-positive bacteria.
Antibiotics
True or False: The Gram stain can provide information about bacterial morphology.
True
What is the function of the peptidoglycan layer in bacteria?
It provides structural support and protection.
Short answer: How does the thickness of the peptidoglycan layer affect the Gram stain results?
Thicker layers retain the crystal violet stain, appearing purple.
Multiple choice: Which of the following bacteria is typically Gram-positive? A) Salmonella B) Staphylococcus C) Neisseria D) Pseudomonas
B) Staphylococcus
