What is the correct order of steps in the Gram stain and the purpose of each step?

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Prepare for the WGU NURS1010 Microbiology Exam with engaging study materials, flashcards, and multiple choice questions. Enhance your understanding with detailed explanations and insights. Get exam-ready today!

Multiple Choice

What is the correct order of steps in the Gram stain and the purpose of each step?

Explanation:
The Gram stain differentiates bacteria by how their cell walls handle dye, using a four-step sequence that relies on a dye, a mordant, a decolorizing agent, and a counterstain. First, crystal violet is applied to all cells, giving a purple color to everything. Then iodine is added as a mordant to form a crystal violet–iodine complex that is larger and more firmly trapped in cells with a thick peptidoglycan layer. Next, alcohol or acetone decolorizes the sample: Gram-positive cells retain the CV–I complex because their thick peptidoglycan layer traps it, whereas Gram-negative cells, with their thinner peptidoglycan and outer membrane, lose the color and become colorless. Finally, safranin is applied as a counterstain to color the decolorized Gram-negative cells pink or red, while the Gram-positive cells remain purple due to the retained CV–I complex.

The Gram stain differentiates bacteria by how their cell walls handle dye, using a four-step sequence that relies on a dye, a mordant, a decolorizing agent, and a counterstain. First, crystal violet is applied to all cells, giving a purple color to everything. Then iodine is added as a mordant to form a crystal violet–iodine complex that is larger and more firmly trapped in cells with a thick peptidoglycan layer. Next, alcohol or acetone decolorizes the sample: Gram-positive cells retain the CV–I complex because their thick peptidoglycan layer traps it, whereas Gram-negative cells, with their thinner peptidoglycan and outer membrane, lose the color and become colorless. Finally, safranin is applied as a counterstain to color the decolorized Gram-negative cells pink or red, while the Gram-positive cells remain purple due to the retained CV–I complex.

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