What structural component is absent in Gram-negative bacteria compared to Gram-positive bacteria?

The choice indicating the absence of an outer membrane in Gram-negative bacteria compared to Gram-positive bacteria is not accurate; Gram-negative bacteria actually have an outer membrane that is a defining characteristic. Instead, the correct distinguishing structural feature when comparing Gram-negative and Gram-positive bacteria is the amount and structure of peptidoglycan in their cell walls.

In Gram-positive bacteria, the cell wall comprises a thick layer of peptidoglycan, which retains the crystal violet dye used in Gram staining, leading to their characteristic purple appearance. Conversely, Gram-negative bacteria have a much thinner peptidoglycan layer situated between the inner and outer membranes.

Thus, when considering structural components, the focus should be on the thin peptidoglycan layer in Gram-negative bacteria as opposed to the thicker layer found in Gram-positive bacteria. The presence of the outer membrane in Gram-negative bacteria actually contributes additional protection and plays a vital role in their overall cell structure, which is not found in Gram-positive bacteria.