Which description correctly characterizes Gram-negative bacteria after Gram staining?

Enhance your microbiology skills for the lab practical exam. Prepare with diverse quizzes and interactive questions, all detailed with hints and answers. Ace your practical exam with comprehensive preparation!

Multiple Choice

Which description correctly characterizes Gram-negative bacteria after Gram staining?

In Gram staining, the cell wall structure drives both color and staining behavior. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane. During the decolorization step, the thin wall can’t retain the crystal violet-iodine complex, and the outer membrane is disrupted, so the cells are decolorized. They then take up the counterstain, safranin, and appear pink/red under the microscope. A thick peptidoglycan layer, as in Gram-positive cells, traps the crystal violet and stays purple. Blue isn’t a standard result in this staining. Therefore, the description that fits is pink with a thin cell wall.

In Gram staining, the cell wall structure drives both color and staining behavior. Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane. During the decolorization step, the thin wall can’t retain the crystal violet-iodine complex, and the outer membrane is disrupted, so the cells are decolorized. They then take up the counterstain, safranin, and appear pink/red under the microscope. A thick peptidoglycan layer, as in Gram-positive cells, traps the crystal violet and stays purple. Blue isn’t a standard result in this staining. Therefore, the description that fits is pink with a thin cell wall.

More practice questions