#1
What is the primary purpose of Gram staining in microbiology?
To differentiate bacteria based on cell wall composition
ExplanationGram staining helps distinguish bacteria by their cell wall structures.
#2
Which color do Gram-positive bacteria appear after Gram staining?
Purple
ExplanationGram-positive bacteria appear purple due to retaining crystal violet stain.
#3
Which stain is used as the primary stain in the Gram staining technique?
Crystal violet
ExplanationCrystal violet is the primary stain in Gram staining.
#4
What is the primary reason for Gram staining bacteria?
To classify bacteria based on cell wall characteristics
ExplanationGram staining is primarily used to classify bacteria based on their cell wall characteristics.
#5
Which step of the Gram staining process involves the application of a counterstain?
Counterstaining
ExplanationCounterstaining involves applying a secondary stain to distinguish Gram-negative bacteria.
#6
Which of the following is NOT a step in the Gram staining process?
Fixation
ExplanationFixation is not a step; instead, it's done before staining to adhere bacteria to the slide.
#7
What component of bacterial cells determines whether they will appear Gram-positive or Gram-negative?
Cell wall composition
ExplanationThe composition of the cell wall dictates whether bacteria appear Gram-positive or Gram-negative.
#8
Who developed the Gram staining technique?
Hans Christian Gram
ExplanationHans Christian Gram developed the Gram staining technique.
#9
Which type of bacteria retain the crystal violet stain in Gram staining?
Gram-positive
ExplanationGram-positive bacteria retain the crystal violet stain.
#10
Which of the following is a characteristic feature of Gram-positive bacteria?
Retains crystal violet stain
ExplanationGram-positive bacteria retain the crystal violet stain.
#11
What is the purpose of the safranin stain in the Gram staining process?
To counterstain Gram-negative bacteria
ExplanationSafranin counterstains Gram-negative bacteria to distinguish them from Gram-positive.
#12
What color do Gram-negative bacteria appear after the counterstain in Gram staining?
Pink
ExplanationGram-negative bacteria appear pink after counterstaining with safranin.
#13
What is the function of the mordant in Gram staining?
To fix the crystal violet stain
ExplanationThe mordant fixes the crystal violet stain to the bacterial cell wall.
#14
Which step of the Gram staining process is most critical for differentiating between Gram-positive and Gram-negative bacteria?
Decolorization
ExplanationDecolorization is crucial for distinguishing between Gram-positive and Gram-negative bacteria.
#15
Which component of Gram-negative bacteria is targeted by the decolorizing agent in Gram staining?
Lipopolysaccharide layer
ExplanationThe decolorizing agent targets the lipopolysaccharide layer in Gram-negative bacteria.
#16
Which of the following bacterial species is known to be Gram-variable, meaning it may appear either Gram-positive or Gram-negative depending on growth conditions?
Listeria monocytogenes
ExplanationListeria monocytogenes can appear Gram-variable depending on growth conditions.
#17
What is the role of the iodine solution in the Gram staining process?
To fix the crystal violet stain
ExplanationIodine solution fixes the crystal violet stain to the bacterial cell wall.