Gram positive bacteria appear_______________?

Correct answer: A. Purple

  • A. Purple
  • B. Red
  • C. Pink
  • D. Blue

Explanation

Gram-positive bacteria retain the crystal violet-iodine complex because their thick peptidoglycan wall is not effectively decolorised, so they appear purple under the microscope. Students may choose red or pink by recalling the colour of Gram-negative bacteria after the counterstain instead.

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