Which statement about Gram-positive bacteria compared to Gram-negative bacteria is true?

Which statement about Gram-positive bacteria compared to Gram-negative bacteria is true?

• A. They have a thick peptidoglycan wall and lack an outer membrane
• B. They have a thick peptidoglycan wall and a prominent outer membrane
• C. They have a thin peptidoglycan wall and no outer membrane
• D. They have an outer membrane with LPS

Answer: (A)

Grams-positive bacteria are defined by a thick peptidoglycan cell wall and the absence of an outer membrane. That thick layer provides rigidity and is why these cells retain crystal violet dye during Gram staining, giving them a purple appearance. The lack of an outer membrane means they do not have the lipopolysaccharide-rich barrier that Gram-negative bacteria possess, which is why options mentioning an outer membrane or LPS don’t apply to Gram-positive cells. In contrast, Gram-negative bacteria have a thinner peptidoglycan layer but do have an outer membrane that includes LPS, contributing to different permeability and antibiotic responses.

Grams-positive bacteria are defined by a thick peptidoglycan cell wall and the absence of an outer membrane. That thick layer provides rigidity and is why these cells retain crystal violet dye during Gram staining, giving them a purple appearance. The lack of an outer membrane means they do not have the lipopolysaccharide-rich barrier that Gram-negative bacteria possess, which is why options mentioning an outer membrane or LPS don’t apply to Gram-positive cells. In contrast, Gram-negative bacteria have a thinner peptidoglycan layer but do have an outer membrane that includes LPS, contributing to different permeability and antibiotic responses.