Key Features of Gram-Negative Bacteria

In microbiology, the classification of bacteria is based on a variety of characteristics, including their morphology and metabolic processes. One such classification involves the use of Gram staining, which distinguishes bacteria into two types: Gram-positive and Gram-negative. Gram-positive bacteria retain a purple color after the Gram stain procedure due to their thick peptidoglycan layer, while Gram-negative bacteria do not retain the stain and appear pink due to their thinner peptidoglycan layer and an outer membrane.

Which of the following statements accurately describes a key feature of Gram-negative bacteria that differentiates them from Gram-positive bacteria?