What structure do Gram-positive bacteria have that is different from Gram-negative bacteria?

Gram-positive bacteria are characterized by having a thick layer of peptidoglycan in their cell walls. This structural component is crucial for the integrity and strength of the bacterial cell, providing protection against osmotic pressure and contributing to the overall shape of the bacterium. The thick peptidoglycan layer also retains the crystal violet stain used in the Gram staining procedure, leading to the distinctive purple coloration of Gram-positive bacteria under a microscope.

In contrast, Gram-negative bacteria possess a much thinner layer of peptidoglycan and have an outer membrane that contains lipopolysaccharides, which is absent in Gram-positive bacteria. The outer membrane serves as an additional barrier and plays a key role in the differentiation between the two groups of bacteria. The distinction in cell wall structure not only influences the staining properties but also affects antibiotic susceptibility, with many antibiotics targeting the peptidoglycan layer specifically.

Thus, the unique structural features of Gram-positive bacteria, particularly their thick peptidoglycan layer, are fundamental to their classification and biological behavior.