Which Gram staining result corresponds to a bacterium with a thick peptidoglycan layer located outside a single cytoplasmic membrane?

• A. Gram-variable because peptidoglycan thickness fluctuates during growth and cannot be predicted from a single stain without electron microscopy.
• B. Gram-positive (purple) because thick, exposed peptidoglycan retains crystal violet-iodine complex.
• C. Gram-negative (pink) because the thin peptidoglycan layer outside two membranes binds crystal violet strongly and appears pink.
• D. Acid-fast because peptidoglycan is replaced by mycolic acids that retain fuchsin after heating.

Answer: (B)