University of Central Florida (UCF) MCB2004 Microbiology for Health Professionals Practice Exam 2

The primary difference between gram-positive and gram-negative bacteria is found in their cell wall structure. Gram-positive bacteria are characterized by having a thick peptidoglycan layer, which is crucial for maintaining their structural integrity and providing resistance to physical stresses. This thick layer retains the crystal violet stain used in the Gram staining procedure, giving gram-positive bacteria their distinct purple coloration.

In contrast, gram-negative bacteria possess a much thinner peptidoglycan layer and are surrounded by an outer membrane that contains lipopolysaccharides. This unique structure not only influences their staining properties but also impacts their susceptibility to antibiotics and the immune response. The presence of the outer membrane in gram-negative bacteria provides an additional barrier that can protect them against certain environmental factors and antimicrobial agents.

Understanding the structural differences in the cell walls of these two categories of bacteria is fundamental in microbiology, particularly in the context of identifying bacterial species and determining appropriate treatment options for infections.