Final answer:
The Gram stain is indeed used to distinguish bacteria based on their cell wall structure, with Gram-positive bacteria appearing purple and Gram-negative bacteria appearing pink after the staining process.
Step-by-step explanation:
The statement that the Gram stain can be used to distinguish bacteria based on the structure of their cell walls is true. Gram staining is a differential staining technique that categorizes bacteria into two groups: Gram-positive and Gram-negative, based on the physical and chemical properties of their cell walls. Gram-positive bacteria have a thick cell wall primarily made of peptidoglycan and teichoic acids, which often appear purple after the stain due to the retention of the crystal violet dye. In contrast, Gram-negative bacteria possess a thinner peptidoglycan layer and have an additional outer membrane containing lipopolysaccharides and lipoproteins, appearing pink after the stain because of the uptake of the counterstain safranin following the decolorization with alcohol.