What is one important distinguishing feature of Gram-negative bacteria?

The distinguishing feature of Gram-negative bacteria is that they possess an outer membrane. This outer membrane is an additional lipid bilayer that encloses the thin peptidoglycan layer, which is a characteristic feature of Gram-negative bacteria. The outer membrane contains lipopolysaccharides (LPS), which play a crucial role in the immune response and contribute to the pathogenicity of many Gram-negative organisms.

In contrast, Gram-positive bacteria have a much thicker peptidoglycan layer without an outer membrane, which is why they stain purple during the Gram staining procedure. The outer membrane found in Gram-negative bacteria also serves as a barrier to certain antibiotics and detergents, making these bacteria more resistant to certain treatments. While the lack of a cell wall is characteristic of certain types of bacteria (such as mycoplasmas), it does not apply to Gram-negative bacteria, which have cell walls with distinct structural features.