Which structural feature differentiates Gram-positive bacteria from Gram-negative bacteria when stained using the Gram staining procedure?

💡 Solution & Explanation

Gram-positive bacteria possess a thick peptidoglycan cell wall that retains the crystal violet-iodine complex during ethanol washing in the Gram staining procedure, appearing purple under a microscope. Gram-negative bacteria have a much thinner peptidoglycan layer coupled with an outer lipid membrane that gets dissolved during decolorization, causing them to absorb the safranin counterstain and appear pink. This structural divergence dictates their differential susceptibility to various antibiotics such as penicillin.