Which bacteria have a smaller amount of peptidoglycan in their cell walls?

Which bacteria have a smaller amount of peptidoglycan in their cell walls?

• A. Gram-positive
• B. Gram-negative
• C. Mycobacteria
• D. Archaea

Answer: (C)

A key idea is how bacterial cell walls vary in composition. Gram-positive bacteria have a thick, extensive peptidoglycan layer, while Gram-negative bacteria have a thinner peptidoglycan layer plus an outer membrane. Mycobacteria stand out because their wall is dominated by a waxy, lipid-rich layer containing long mycolic acids, with the peptidoglycan portion present but in a relatively smaller amount compared to the overall wall. This lipid-rich barrier makes the peptidoglycan portion proportionally smaller, even though some peptidoglycan is still there, embedded with arabinogalactan. Archaea aren’t bacteria and often lack peptidoglycan altogether, which is a different scenario. So the organism with the least peptidoglycan content in its wall among these options is the mycobacteria.

A key idea is how bacterial cell walls vary in composition. Gram-positive bacteria have a thick, extensive peptidoglycan layer, while Gram-negative bacteria have a thinner peptidoglycan layer plus an outer membrane. Mycobacteria stand out because their wall is dominated by a waxy, lipid-rich layer containing long mycolic acids, with the peptidoglycan portion present but in a relatively smaller amount compared to the overall wall. This lipid-rich barrier makes the peptidoglycan portion proportionally smaller, even though some peptidoglycan is still there, embedded with arabinogalactan. Archaea aren’t bacteria and often lack peptidoglycan altogether, which is a different scenario. So the organism with the least peptidoglycan content in its wall among these options is the mycobacteria.