Multiple choice

Which staining method is used to visualise gram positive bacteria?

  1. Negative simple staining

  2. Acid fast staining

  3. Gram staining

  4. Positive simple staining

  5. Neutral staining
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gram Staining was developed by a Danish physician Hans Christian Gram in 1884. It helps to categorize bacteria in two groups, Gram Positive and Gram Negative. The smear of bacteria is prepared and stained with crystal violet. The smear is dipped in a mordant iodine solution which helps in strong adherence of the stain, and destaining is done with the help of ethanol or acetone.Gram Positive bacteria retain a purple colour of crystal violet, while Gram Negative bacteria lose purple colour. To stain Gram Negative bacteria, a counter stain safranin is used, so that they appear pinkish or reddish.

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