Suppose you perform a Gram stain of a mixed culture of Gram-positive and Gram-negative cells, and afterward you realize that you omitted the iodine step. What would you expect to see if you observed the slide under the microscope?

Question

Quizplus · Accepted Answer

Omitting the iodine step in a Gram stain procedure prevents the crystal violet dye from forming a complex with iodine, which is necessary for the dye to be trapped in the thick peptidoglycan layer of Gram-positive cells. Without this step, both Gram-positive and Gram-negative cells will not retain the crystal violet and will appear pink after counterstaining with safranin.

Suppose You Perform a Gram Stain of a Mixed Culture