Which feature distinguishes Gram negative bacteria?

The distinguishing feature of Gram-negative bacteria is indeed the presence of a thin peptidoglycan layer in their cell walls. Gram-negative bacteria have a more complex structure compared to Gram-positive bacteria. The thin peptidoglycan layer is sandwiched between the inner cytoplasmic membrane and an outer membrane, which is characteristic of Gram-negative bacteria.

This structural configuration is significant because it influences the bacteria's response to Gram staining procedures, ultimately leading to their characteristic pink coloration when subjected to this test. The outer membrane contains lipopolysaccharides, which can trigger a strong immune response and can serve as a barrier to certain antibiotics and detergents.

In contrast, Gram-positive bacteria are defined by a thick peptidoglycan layer, which retains the crystal violet stain used in Gram staining, resulting in a purple coloration. The absence of an outer membrane is another key differentiator that highlights the differences between these two groups of bacteria, but it does not apply to the defining characteristic of Gram negativity. Additionally, the presence of spores is not relevant to whether a bacterium is classified as Gram-negative or not, as spore formation can occur in certain Gram-positive and even some Gram-negative organisms, depending on their species and type.