QuestionSBA
QuestionChoice
The first stain is purple (the cyrstal violet stain). This is washed away, and then the sample is stained pink (the safranin or Carbol fuchsin stain).
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c
The bacteria is stained pink and then purple
QuestionChoice
Gram-negative bacteria appear pink with gram-staining as the crystal violet-iodine purple stain is washed away from their cell wall, and they then turn pink with the counterstain.
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e
Gram-negative bacteria appear purple
QuestionChoice
It is actually the cell wall that determines the staining of bacteria, and hence the colour of the bacteria.
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b
It is the cell membrane which determines the colour of the bacteria
QuestionChoice
The first stain added in a gram stain is crystal violet stain, which will stain all of the bacteria present purple. Next, an iodine stain is added. The iodine forms a complex with the crystal violet stain to stabilise it. Thirdly, alcohol or acetone is added which will wash the crystal violet-iodine complex away from the gram-negative bacteria. Lastly, a safranin or Carbol fuchsin stain is added to stain the gram-negative bacteria pink.
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a
Iodine binds the crystal violet stain within the cell wall
QuestionChoice
It is actually either ethanol or acetone is used for decolourisation.
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d
Nitrofurantoin is used to decolourise the sample before the final stain is added
Concept
Chapter
2693
5780
Gram-positive and Gram-negative bacteria classification
Topic
148
Microbiology
17296
Which of the following is true regarding the process of gram staining bacteria?
a