Which one of the following is NOT a feature of gram-negative bacteria?

The distinguishing feature of gram-negative bacteria is their unique cell wall structure, which is characterized by a thin peptidoglycan layer surrounded by an outer membrane. The presence of a thick peptidoglycan layer is a hallmark of gram-positive bacteria, not gram-negative.

In gram-negative bacteria, the thin peptidoglycan layer is located between the inner cytoplasmic membrane and the outer membrane, which provides structural integrity but is significantly less thick compared to that of gram-positive bacteria. This thin layer has important implications for the bacteria's susceptibility to antibiotics, as certain antibiotics target the peptidoglycan.

The outer membrane of gram-negative bacteria serves as a barrier that can protect against certain environmental threats and is also where lipopolysaccharides are found. These lipopolysaccharides are integral to the biology of gram-negative bacteria, contributing to immune response activation in the host.

The periplasmic space is another feature present in gram-negative bacteria, existing between the inner and outer membranes and containing various enzymes and proteins involved in transport and degradation processes.

Thus, the thick peptidoglycan layer is the correct identification as a non-feature of gram-negative bacteria, contrasting with the other characteristics that are indeed present in their structure