Which color do Gram-negative bacteria typically appear after Gram staining?

Study for the PMLS History of Medical Technology Test. Explore flashcards and multiple choice questions, each question is accompanied by hints and explanations. Get prepared for your exam!

Grams staining hinges on cell wall differences to separate bacteria into two groups. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane that donates less ability to retain the crystal violet-iodine complex during the decolorization step. After they are decolorized, they take up the counterstain, usually safranin, which gives them a pink to red appearance under the microscope. That pink/red outcome is characteristic of Gram-negative organisms. In contrast, Gram-positive bacteria keep the purple/violet stain because their thick peptidoglycan layer traps the dye. The yellow or blue colors aren’t produced by this staining sequence, so they don’t represent the typical Gram stain results.